[domain-deletion]Introduce a new API for domain deletion

[gazi-yestemirova]

Detailed Description
[In-depth description of the changes made to the schema or interfaces, specifying new fields, removed fields, or modified data structures]

• Added new DeleteDomain API to permanently remove domain records
• The API requires the domain to be in DEPRECATED status
• Added validation to ensure domain has no running workflows before deletion
• Added error handling for various failure scenarios:
  - Domain not found
  - Domain not in deprecated state
  - Domain has existing workflow history
  - Deletion operation failures
  Added unit tests covering success and failure cases

Impact Analysis

• Backward Compatibility:
  The change is backward compatible as it only adds a new API endpoint
  Existing domain operations (Register, Update, Deprecate) remain unchanged
  No changes to existing data structures or schemas

• Forward Compatibility:
  The change is forward compatible
  New clients can use the DeleteDomain API while old clients continue to work with existing APIs
  No breaking changes to existing interfaces or data structures

Testing Plan

• Unit Tests: Added comprehensive unit tests in common/domain/handler_test.go & service/frontend/api/domain_handlers_test.go
• Persistence Tests: [If the change is related to a data type which is persisted, do we have persistence tests covering the change?]
• Integration Tests: [Do we have integration test covering the change?]
• Compatibility Tests: [Have we done tests to test the backward and forward compatibility?]

Rollout Plan

• What is the rollout plan? Deploy to dev & staging environments first. Deploy to prod environments in waves.
• Does the order of deployment matter? No
• Is it safe to rollback? Does the order of rollback matter? Safe to rollback as it's an additive change
• Is there a kill switch to mitigate the impact immediately? No specific kill switch needed

[3vilhamster]

Where does this check exists? Is there a test on this?

[gazi-yestemirova]

yes, it was added later under service/frontend/api/domain_handlers.go DeleteDomain()

[3vilhamster]

nit:
It is better to call subtests with underscope:
success_delete_deprecated_domain

This way, when a test fails, you can easily find the failed case.
When you use spaces and dashes, it will not be apparent which test case caused the failure.
And I think it will look like:
TestDeleteDomain/success_-_delete_deprecated_domain