Implement Error Handling in backend - T415715 Micro-Task

[Mariam22-hub]

This PR addresses this backend improvement tasks:

Error Handling & Observability — strengthen exception handling, introduce structured logging, standardise API error responses, and capture async task errors

Key Changes

• Standardized API Responses

  • Unified response format across all endpoints, by adding generic functions (error_response, success_response) in utils.py
  • Removed inconsistent patterns

• Request Handling

  • Added input validation and safe JSON parsing (get_json(silent=True))
  • Guarded URL parsing to prevent runtime errors

• Consistent Error Handling

  • Mapped domain-specific exceptions to appropriate HTTP status codes, e.g:
    • FileNotFoundOnWikiError → 404
    • ImageDownloadError, APIRequestError → 502
  • Clean handling of CSRF and upload-related errors

• Codebase Refactor

  • Moved duplicated shared logic (e.g. _fetch_csrf_token) to generic functions

• Structured Logging

  • Replaced ad-hoc logging.basicConfig calls with a centralised logger configuration. All modules now call get_logger(__name__) to get a consistently configured logger.

• Config File

  • Replaced all os.environ reads and hardcoded settings with a single config.ini file read at import time via Python's built-in configparser.

• Tests

  • Added comprehensive unit tests, using pytest, to test all flows for each function and api in app.py, utils.py, tasks.py, exceptions.py, and logger.py