global class StackOverflowPostDataSourceProvider
        extends DataSource.Provider {

   
    override global List<DataSource.AuthenticationCapability>
    getAuthenticationCapabilities() {
        List<DataSource.AuthenticationCapability> capabilities =
                new List<DataSource.AuthenticationCapability>();
        capabilities.add(
                DataSource.AuthenticationCapability.ANONYMOUS);
        return capabilities;
    }
    override global List<DataSource.Capability>
    getCapabilities() {
        List<DataSource.Capability> capabilities =
                new List<DataSource.Capability>();
        capabilities.add(DataSource.Capability.ROW_QUERY);
        return capabilities;
    }

    override global DataSource.Connection getConnection(
            DataSource.ConnectionParams connectionParams) {
        return new 
            StackOverflowDataSourceConnection(connectionParams);
    }
}

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_connector_example_stackoverflow.htm

Apex class and call from trigger

Apex class and call from trigger