Add comprehensive form and JSON parameter parsing middleware

[wesen]

Adds robust middleware for handling form data and JSON request parameters in Parka:

Core Changes:

• Implements structured FormMiddleware for handling multipart form data and file uploads
• Adds JSONBodyMiddleware for processing JSON POST request bodies
• Both middlewares support proper temporary file cleanup
• Thread-safe file management with mutex protection
• Comprehensive parameter type handling including arrays and objects

Features:

• Safe temporary file handling with automatic cleanup
• Support for file-like parameters in both form and JSON requests
• Array parameter handling with proper type conversion
• Required parameter validation
• Structured error handling and reporting

Improvements:

• Refactored form handling into a proper middleware struct
• Added comprehensive test coverage
• Added detailed documentation and usage examples
• Improved error messages and validation

Breaking Changes:

• UpdateFromFormQuery now uses structured middleware internally
• Middleware execution order may need to be adjusted in existing code