fix: DSVError are not JSON serializable

[CJHwong]

Reason

The recent modifications have led to problems with the Django request process when the DSVError exception is triggered.

Changes

1. Convert All Python Exceptions to Strings: Transform any Python exceptions into string format before providing the response.
2. Revert to Original Name if Needed: If dsv_feature.spec_name is not provided, use the original name as a fallback option.

Test Scope

Checks

• Unit tests are included or not applicable.