feat!(#113): change validation errors to 422 and add custom error messages

[usernane]

Summary

Change validation error HTTP status from 404 to 422 (Unprocessable Entity) and add support for custom per-parameter error messages.

Motivation

404 means "resource not found" — using it for validation errors is semantically incorrect and confuses API consumers. Additionally, the error response only listed parameter names with no human-readable explanation. Fixes #113.

Changes

• Status code: ErrorResponse::invalidParams() and missingParams() now return 422
• Custom messages: Added ParamOption::MESSAGE option and RequestParameter::getMessage()/setMessage()
• Attribute support: #[RequestParam(..., message: 'Custom error')]
• Response format: {"message": "Validation failed", "type": "error", "http-code": 422, "more-info": {"errors": {"field": "message"}}}
• Auto-generated messages: If no custom message set, uses "Invalid value for parameter 'X'." or "Required parameter 'X' is missing."
• Backward compat for ErrorResponse: Accepts both string names and RequestParameter objects

UI Changes

N/A

How to Test / Verify

php vendor/bin/phpunit tests/WebFiori/Tests/Http/ValidationErrorMessagesTest.php

9 new tests, 19 assertions. Full suite: 583 tests pass.

Breaking Changes and Migration Steps

Status code changed from 404 to 422 for validation errors. Clients checking for 404 on invalid/missing parameters need to check for 422 instead.

Response format changed: more-info now contains {"errors": {"field": "message"}} instead of {"invalid": ["field"]} or {"missing": ["field"]}.

Checklist

• I reviewed my own diff before requesting review
• My commits follow Conventional Commits
• The title of the pull request follows Conventional Commits
• I added/updated tests (or explained why not)
• I updated docs (if needed)
• I ran lint/cs-fixer (if applicable)
• I considered backward compatibility
• I considered security

Related issues

Closes #113

[sonarqubecloud]

Quality Gate failed

Failed conditions
14.9% Duplication on New Code (required ≤ 6%)

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.77%. Comparing base (2793917) to head (26341e2).

Additional details and impacted files

@@             Coverage Diff              @@
##                dev     #135      +/-   ##
============================================
+ Coverage     93.75%   93.77%   +0.01%     
- Complexity     1317     1322       +5     
============================================
  Files            39       39              
  Lines          3218     3227       +9     
============================================
+ Hits           3017     3026       +9     
  Misses          201      201              

Flag	Coverage Δ
php-8.3	93.77% <100.00%> (+0.01%)	⬆️

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