Refactor OAuth2 Authorization Request Validation Logic for Improved Readability, Reusability, and Error Handling

[Raisul191491]

This pull request introduces several improvements to the OAuth2 validation logic to enhance code clarity, maintainability, and error handling:

1. Request Method Validation:

   • Refactored request method validation to encapsulate logic in a reusable function (CheckAuthorizeRequestMethod).
   • Introduced descriptive variables for better readability.

2. Response Type Validation:

   • Simplified response type validation by delegating logic and error handling to CheckResponseType.

3. Code Challenge Validation:

   • Removed unnecessary logic in code challenge and code challenge method validation.
   • Updated validation logic and error messages for clarity and precision.

4. Error Handling Improvements:

   • Introduced more descriptive error messages to make debugging easier.