fix: Consistent response format

[ekas-7]

Standardize API Response Format

Description

This PR addresses issue #119 "Streamline and harmonize simple responses across API routes" by implementing a consistent response format across all endpoints in the Folksonomy API.

Previously, the API returned responses in various formats:

• Simple string responses like "ok"
• JSON with {"detail": "message"}
• Nested JSON with {"detail": {"msg": "message"}}

This inconsistency made it difficult for API consumers to handle responses predictably.

Changes Made

1. Added a SimpleResponse model in models.py with a standardized structure:

   class SimpleResponse(BaseModel):
       detail: Dict[str, str]

2. Updated the PingResponse model to follow the same structure.

3. Modified all endpoints that return simple responses to use this consistent format:

   • POST /product endpoint (create)
   • PUT /product endpoint (update)
   • DELETE /product/{product}/{k} endpoint (delete)
   • GET /ping endpoint

4. Updated error responses to follow the same format.

5. Fixed empty array responses to return [] instead of null when no data is found.

6. Added response_model=SimpleResponse parameter to appropriate API routes for better documentation.

Example Changes

Before:

return "ok"  # or return {"message": "ok"}, etc.

After:

return {"detail": {"msg": "Tag created successfully"}}

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 94.48%. Comparing base (b9cda65) to head (cef15cf).
Report is 75 commits behind head on main.

Files with missing lines	Patch %	Lines
folksonomy/api.py	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #259      +/-   ##
==========================================
- Coverage   95.06%   94.48%   -0.58%     
==========================================
  Files           5        5              
  Lines         324      381      +57     
==========================================
+ Hits          308      360      +52     
- Misses         16       21       +5     

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[alexgarel]

@ekas-7 per se it's a good idea, but as already said on other PRs we can't change the API without first verifying it does not break:

• the mobile app
• the open food facts website.

So to propose this PR, you must verify if it's causing problem for them, or not.

[ekas-7]

I will propose this in an issue @alexgarel in both repos

[ekas-7]

Opened an issue in smooth app
openfoodfacts/smooth-app#6468
for this @alexgarel

[ekas-7]

Opened in Web as well
openfoodfacts/openfoodfacts-web#696
for this @alexgarel