tests: implement unit tests for controllers and services

[Q-Niranjan]

This PR improves test coverage for the OpenG2P Portal API, with a focus on controllers, services, and exception handling. The tests ensure key functionalities like authentication, file handling, program management, and error scenarios are robustly covered.

Controllers: Auth, Discovery, File, Form, OAuth, and Program controllers tested.
Services: Document File, Form, Membership, Partner, and Program services tested.
Exception Handling: Validates error scenarios and authorization flows.

Impact: Ensures reliable API behavior, prevents regressions, and improves maintainability.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.02%. Comparing base (2ab1362) to head (55f4b3a).
Report is 7 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop      #29       +/-   ##
============================================
+ Coverage    55.21%   87.02%   +31.80%     
============================================
  Files           38       49       +11     
  Lines         1304     2273      +969     
  Branches        92       93        +1     
============================================
+ Hits           720     1978     +1258     
+ Misses         584      253      -331     
- Partials         0       42       +42     

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