Create custom field on Contact for "Sequence Number". Create trigger to manage sequence of Contacts on an Account. Handle all the events and cases.

# Re-order sequence number when new records are inserted
# Re-order sequence number when records are updated
# Re-order sequence number when records are deleted
# In case of re-parenting, add record at last position
# In case of undelete, add record at last position

- Create test sheet for all the test cases
- Create test methods for all the test cases, please refer acceptance criteria                                                                                                                                                                                                                      1) Bulk Re-parenting
2) Bulk update sequence number
3) Remove Parent
4) Bulk (Create, Update, Delete, Undelete)
5) update legacy (Existing) records

Test class coverage should be above 95%