Duplicate Issue History Entries When Adding Same Test to Test Set via REST API

Duplicate Issue History Entries When Adding Same Test to Test Set via REST API.

Steps to Reproduce:

1. Create a Test Set.
2. Associate a Test to the Test Set using the REST API endpoint: /rest/raven/1.0/api/testset/{testSetKey}/test.
3. Confirm that the Test is successfully associated with the Test Set.
4. Check the Issue History to ensure a new entry was added.
5. Attempt to associate the same Test to the Test Set again using the same REST API endpoint.
6. Observe that another entry appears in the Issue History.

Expected Behavior:
If a Test is already associated with a Test Set, the operation to add the Test again should be discarded to prevent duplicate entries in the Issue History.
The expected behavior should be consistent with the User Interface, which displays the message:

Test with key <ISSUE_KEY> is already associated with this Test Set.