I want to access the default tab set for an app so that I can automatically redirect the user there. I have checked DescribeTabSetResult class: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_class_schema_describetabsetresult.htm
But it does not have any method to get the default tab. 

Thank you!

Trigger
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trigger paymentinfo on Opportunity (after update) {
  for (Opportunity op : Trigger.new) {
    if ((op.CC__c != null) || (op.Routing_Number__c != null)) {
      if (paymentinfoTriggerHandler.ShowRun == true) {
       paymentinfoTriggerHandler handler = new paymentinfoTriggerHandler(); 
        handler.sendCardToTPro(op);
      }
    }
  }
}
---------------------------------------------------------------
handler

public class paymentinfoTriggerHandler {
    public paymentinfoTriggerHandler () {}
    Public Static boolean ShowRun = true;
    public void sendCardToTPro(Opportunity op) {
        if (op.TPro_Success__c != 'true') {
            //if( ! System.isBatch()  &&  ! System.isFuture() )
                paymentinfoTriggerHandler .send(op.Id);    
        }
    }
    @future(callout=true)
    STATIC public void send(String opid) {
        ShowRun = false;
        Opportunity op = [SELECT Id,Card_Holder_s_Name__c,CC__c,CC_Expiration_Date__c,Account.IntacctID__c,
                                 Org_Name__c,Card_Holder_s_Street__c,Card_Holder_s_Street_2__c,Card_Holder_s_City__c,Card_Holder_s_State__c,Card_Holder_s_Zip__c,
                                 Account.Organization_Email_Address__c, Account.Primary_Contact_Email__c,Event_Code__c,Routing_Number__c,Accounting_Number__c,TPro_Success__c,TPro_AuthID__c,TPro_CC_StoredAccountID__c
                          FROM Opportunity
                          WHERE Id = :opid];
        
        op.TPro_Success__c = null;
        op.TPro_CC_StoredAccountID__c = null;
        
        HttpRequest authRequest = new HttpRequest();
        authRequest.setHeader('Content-Type', 'text/xml');
        authRequest.setEndpoint('URL');
        authRequest.setMethod('POST');
        string xml = '';
        xml += '<request>';
        xml += '  <authentication>';
        xml += '    <user>';
        xml += '      <gateway></gateway>';
        xml += '      <emailaddress></emailaddress>';
        xml += '      <password></password>';
        xml += '      <application>Salesforce</application>';
        xml += '      <version>1.0.0</version>';
        xml += '    </user>';
        xml += '  </authentication>';
        xml += '  <content continueonfailure="true">';
        xml += '    <update>';
        xml += '      <customer refname="customer">';
        xml += '        <name>' + op.Account.IntacctID__c + '</name>';
        xml += '        <displayname>' + op.Org_Name__c + '</displayname>';
        xml += '      </customer>';
        xml += '    </update>';
        xml += '    <if condition="{!customer.responsestatus!} != \'success\'">';
        xml += '      <create>';
        xml += '        <customer refname="customer">';
        xml += '          <name>' + op.Account.IntacctID__c + '</name>';
        xml += '          <displayname>' + op.Org_Name__c + '</displayname>';
        xml += '        </customer>';
        xml += '      </create>';
        xml += '    </if>';
        xml += '    <if condition="{!customer.responsestatus!} = \'success\'">';
        xml += '      <update>';
        xml += '        <contact refname="contact">';
        xml += '          <name>B_{!customer.name!}</name>';
        xml += '          <customer>{!customer.id!}</customer>';
        xml += '          <contacttype>billing</contacttype>';
        if (op.Org_Name__c != null)
          xml += '          <companyname>' + op.Org_Name__c + '</companyname>';
        if (op.Card_Holder_s_Name__c != null) {
          xml += '          <firstname>' + op.Card_Holder_s_Name__c + '</firstname>';
          xml += '          <lastname>' + op.Card_Holder_s_Name__c + '</lastname>';
        }
        if (op.Card_Holder_s_Street__c != null)
          xml += '          <address1>' + op.Card_Holder_s_Street__c + '</address1>';
        if (op.Card_Holder_s_Street_2__c != null)
          xml += '          <address2>' + op.Card_Holder_s_Street_2__c + '</address2>';
        if (op.Card_Holder_s_City__c != null)
          xml += '          <city>' + op.Card_Holder_s_City__c + '</city>';
        if (op.Card_Holder_s_State__c != null)
          xml += '          <state>' + op.Card_Holder_s_State__c + '</state>';
        if (op.Card_Holder_s_Zip__c != null)
          xml += '          <zipcode>' + op.Card_Holder_s_Zip__c + '</zipcode>';
        xml += '          <country>United States</country>';
        if (op.Account.Organization_Email_Address__c != null)
          xml += '          <email1>' + op.Account.Organization_Email_Address__c + '</email1>';
        xml += '        </contact>';
        xml += '      </update>';
        xml += '    </if>';
        xml += '    <if condition="{!contact.responsestatus!} != \'success\'">';
        xml += '      <create>';
        xml += '        <contact refname="contact">';
        xml += '          <name>B_{!customer.name!}</name>';
        xml += '          <customer>{!customer.id!}</customer>';
        xml += '          <contacttype>billing</contacttype>';
        if (op.Org_Name__c != null)
          xml += '          <companyname>' + op.Org_Name__c + '</companyname>';
        if (op.Card_Holder_s_Name__c != null) {
          xml += '          <firstname>' + op.Card_Holder_s_Name__c + '</firstname>';
          xml += '          <lastname>' + op.Card_Holder_s_Name__c + '</lastname>';
        }
        if (op.Card_Holder_s_Street__c != null)
          xml += '          <address1>' + op.Card_Holder_s_Street__c + '</address1>';
        if (op.Card_Holder_s_Street_2__c != null)
          xml += '          <address2>' + op.Card_Holder_s_Street_2__c + '</address2>';
        if (op.Card_Holder_s_City__c != null)
          xml += '          <city>' + op.Card_Holder_s_City__c + '</city>';
        if (op.Card_Holder_s_State__c != null)
          xml += '          <state>' + op.Card_Holder_s_State__c + '</state>';
        if (op.Card_Holder_s_Zip__c != null)
          xml += '          <zipcode>' + op.Card_Holder_s_Zip__c + '</zipcode>';
        xml += '          <country>United States</country>';
        if (op.Account.Organization_Email_Address__c != null)
          xml += '          <email1>' + op.Account.Organization_Email_Address__c + '</email1>';
        xml += '        </contact>';
        xml += '      </create>';
        xml += '    </if>';
        if ((op.CC__c != null) && (op.CC__c.trim().length() > 0) && (op.CC_Expiration_Date__c != null) && (op.CC_Expiration_Date__c.trim().length() > 0)) {
        xml += '    <if condition="{!contact.responsestatus!} = \'success\'">';
        xml += '      <update>';
        xml += '        <storedaccount refname="cc">';
        xml += '          <name>' + op.Event_Code__c + '_CC</name>';
        xml += '          <displayname>' + op.Event_Code__c + '_CC</displayname>';
        xml += '          <customer>{!customer.id!}</customer>';
        xml += '          <contact>{!contact.id!}</contact>';
        xml += '          <creditcard>';
        xml += '            <keyed>';
        if (op.CC__c != null)
          xml += '              <cardholdernumber>' + op.CC__c + '</cardholdernumber>';
        if (op.Card_Holder_s_Name__c != null)
          xml += '              <cardholdername>' + op.Card_Holder_s_Name__c + '</cardholdername>';
        if (op.CC_Expiration_Date__c != null) {
          xml += '              <expiresmonth>' + op.CC_Expiration_Date__c.substring(0, 2) + '</expiresmonth>';
          xml += '              <expiresyear>' + '20' + op.CC_Expiration_Date__c.substring(op.CC_Expiration_Date__c.length() - 2, op.CC_Expiration_Date__c.length()) + '</expiresyear>';
        }
        xml += '            </keyed>';
        xml += '          </creditcard>';
        xml += '        </storedaccount>';
        xml += '      </update>';
        xml += '    </if>';
        xml += '    <if condition="{!cc.responsestatus!} != \'success\'">';
        xml += '      <create>';
        xml += '        <storedaccount refname="cc">';
        xml += '          <name>' + op.Event_Code__c + '_CC</name>';
        xml += '          <displayname>' + op.Event_Code__c + '_CC</displayname>';
        xml += '          <customer>{!customer.id!}</customer>';
        xml += '          <contact>{!contact.id!}</contact>';
        xml += '          <creditcard>';
        xml += '            <keyed>';
        if (op.CC__c != null)
          xml += '              <cardholdernumber>' + op.CC__c + '</cardholdernumber>';
        if (op.Card_Holder_s_Name__c != null)
          xml += '              <cardholdername>' + op.Card_Holder_s_Name__c + '</cardholdername>';
        if (op.CC_Expiration_Date__c != null) {
          xml += '              <expiresmonth>' + op.CC_Expiration_Date__c.substring(0, 2) + '</expiresmonth>';
          xml += '              <expiresyear>' + '20' + op.CC_Expiration_Date__c.substring(op.CC_Expiration_Date__c.length() - 2, op.CC_Expiration_Date__c.length()) + '</expiresyear>';
        }
        xml += '            </keyed>';
        xml += '          </creditcard>';
        xml += '        </storedaccount>';
        xml += '      </create>';
        xml += '    </if>';
        }
        if ((op.Accounting_Number__c != null) && (op.Accounting_Number__c.trim().length() > 0) && (op.Routing_Number__c != null) && (op.Routing_Number__c.trim().length() > 0)) {
        xml += '    <if condition="{!contact.responsestatus!} = \'success\'">';
        xml += '      <update>';
        xml += '        <storedaccount refname="ach">';
        xml += '          <name>' + op.Event_Code__c + '_ACH</name>';
        xml += '          <displayname>' + op.Event_Code__c + '_ACH</displayname>';
        xml += '          <customer>{!customer.id!}</customer>';
        xml += '          <contact>{!contact.id!}</contact>';
        xml += '          <ach>';
        if (op.Card_Holder_s_Name__c != null)
          xml += '            <AccountHolder>' + op.Card_Holder_s_Name__c + '</AccountHolder>';
        if (op.Accounting_Number__c != null)
          xml += '            <AccountNumber>' + op.Accounting_Number__c + '</AccountNumber>';
        xml += '            <PaymentType>Single</PaymentType>';
        if (op.Routing_Number__c != null)
          xml += '            <RoutingNumber>' + op.Routing_Number__c + '</RoutingNumber>';
        xml += '            <SecCode>CCD</SecCode>';
        xml += '          </ach>';
        xml += '        </storedaccount>';
        xml += '      </update>';
        xml += '    </if>';
        xml += '    <if condition="{!ach.responsestatus!} != \'success\'">';
        xml += '      <create>';
        xml += '        <storedaccount refname="ach">';
        xml += '          <name>' + op.Event_Code__c + '_ACH</name>';
        xml += '          <displayname>' + op.Event_Code__c + '_ACH</displayname>';
        xml += '          <customer>{!customer.id!}</customer>';
        xml += '          <contact>{!contact.id!}</contact>';
        xml += '          <ach>';
        if (op.Card_Holder_s_Name__c != null)
          xml += '            <AccountHolder>' + op.Card_Holder_s_Name__c + '</AccountHolder>';
        if (op.Accounting_Number__c != null)
          xml += '            <AccountNumber>' + op.Accounting_Number__c + '</AccountNumber>';
        xml += '            <PaymentType>Single</PaymentType>';
        if (op.Routing_Number__c != null)
          xml += '            <RoutingNumber>' + op.Routing_Number__c + '</RoutingNumber>';
        xml += '            <SecCode>CCD</SecCode>';
        xml += '          </ach>';
        xml += '        </storedaccount>';
        xml += '      </create>';
        xml += '    </if>';
        }
        xml += '  </content>';
        xml += '</request>';
        authRequest.setBody(xml);
        //authRequest.setCompressed(true); 
        
        Http http = new Http();
        HttpResponse res = http.send(authRequest);
        DOM.Document authResponse = res.getBodyDocument();  
        for(DOM.XmlNode node :authResponse.getRootElement().getChildElements()){
          if(node.getName() == 'authentication'){
            if (node.getAttributeValue('responsestatus', '') != 'success') {
              processError(op, node);              
            }
          }
          else if(node.getName() == 'content'){
            if (processUpdateCreate(op, 'customer','customer',node) == true) {
              if (processUpdateCreate(op, 'contact','contact',node) == true) {              
                processUpdateCreate(op, 'storedaccount','cc',node);
                processUpdateCreate(op, 'storedaccount','ach',node);
              }
            }
          }
        }
        update op;
    }
    STATIC public void processError(Opportunity op, DOM.XmlNode errorNode) {
      for(DOM.XmlNode node :errorNode.getChildElements()){
        if (node.getName() == 'errors') {
          for(DOM.XmlNode enode :node.getChildElements()){
            if (enode.getName() == 'error') {
              string enumber = '';
              string edescription = '';
              for(DOM.XmlNode enode2 :enode.getChildElements()){
                if (enode2.getName() == 'number')
                  enumber = enode2.getText();
                else if (enode2.getName() == 'description')
                  edescription = enode2.getText();
              }
              if (op.TPro_Success__c == null)
                op.TPro_Success__c = edescription + ' (' + enumber + ')';
              else
                op.TPro_Success__c = op.TPro_Success__c + ',' + edescription + ' (' + enumber + ')';
            }
          }
        }
      }
    }
    STATIC public Boolean processUpdateCreate(Opportunity op, string nodename, string refname, DOM.XmlNode ucNode) {
      Boolean isUpdated = false;
      Boolean isCreated = false;
      DOM.XmlNode tempCreated = null;
      DOM.XmlNode tempUpdated = null;
      for(DOM.XmlNode subnode :ucnode.getChildElements()){
        if (subnode.getName() == 'update') {
          for(DOM.XmlNode updatenode :subnode.getChildElements()){
            if (nodename == updatenode.getName()) {
              tempUpdated = updatenode;
              if ((updatenode.getAttributeValue('responsestatus', '') == 'success') && (updatenode.getAttributeValue('refname', '') == refname)) {
                isUpdated = true;
                if (refname == 'cc') {
                  for(DOM.XmlNode idnode :updatenode.getChildElements()){
                    if (idnode.getName() == 'id') {
                      op.TPro_CC_StoredAccountID__c = idnode.getText();
                    }
                  }                 
                }
              }
            }
          }
        }
        else if (subnode.getName() == 'create') {
          for(DOM.XmlNode createnode :subnode.getChildElements()){
            if (nodename == createnode.getName()) {
              tempCreated = createnode;
              if ((createnode.getAttributeValue('responsestatus', '') == 'success') && (createnode.getAttributeValue('refname', '') == refname)) {
                isCreated = true;
                if (refname == 'cc') {
                  for(DOM.XmlNode idnode :createnode.getChildElements()){
                    if (idnode.getName() == 'id') {
                      op.TPro_CC_StoredAccountID__c = idnode.getText();
                    }
                  }                 
                }
              }
            }
          }
        }
      } 
      if ((isUpdated == false) && (isCreated == false)) {
        if (tempCreated != null)
          processError(op, tempCreated);
        else if (tempUpdated != null)
          processError(op, tempUpdated);
        return (false);
      }         
      string tempstatus = '';
      if (isUpdated == true)
        tempstatus = 'Updated';
      else if (isCreated == true)
        tempstatus = 'Created';
      if (op.TPro_Success__c == null)
        op.TPro_Success__c = 'Successfully ' + tempstatus + ': ' + refname;
      else
        op.TPro_Success__c = op.TPro_Success__c + ',Successfully ' + tempstatus + ': ' + refname;
      update op; 
      return (true);
    }
}

hi...m new to sf.. can i get the code to test the rest api callout ...its urgent to delicer...thanks a lot !!!