Update enums for entity_type in API models and adjust POST /borrowers endpoint

Updated endpoints

• POST /borrowers: Updated enum values for entity_type property in related definitions affecting the request payload.

Other Changes

• Modified entity_type enum values across multiple definitions (APICreateDirector, APIDirector, LoanApiEvent):
  • Reordered and renamed several enum entries, for example:
    • 'installment' changed to 'financial_product'
    • 'invoice' changed to 'installment'
    • 'loan' changed to 'invoice'
    • 'loan_log' changed to 'loan'
    • and others accordingly
  • Added a new enum value 'sandbox_invoice' at the end of the list.

These changes impact any client code relying on these enums for the specified API models.