Refactor request body validation using decorator

[Aadesh-Baral]

This PR adds the necessary component to fix Task 1 of #5910

• Creates a decorator which can be used to validate the request body against a DTO class.
  • This decorator can be applied to the route handler that requires request validation.
  • This decorator validates the request using the provided DTO class and stores the validated DTO instance in request.validated_dto.
• Adds a function to fetch validation errors from Schematics DataError exception class so that we can return what and where error occurred during request validation.

Sample validation error :

@validate_request(ProjectCreateDTO)
def post():
validated_dto = request.validated_dto # request.validated_dto will be set in the decorator after validating request against dto ProjectCreateDTO

If the validation error occurs due to missing project description and instruction we will have error response like:

{
  "error":{
    "code": 400,
    "sub_code": "BAD_REQUEST",
    "message": "The request was invalid or cannot be otherwise served."
    "details": {
      "field_errors": {
        "field": "description", "message": "This field is required",
        "field": "instruction", "message": "This field is required"
      }
    }
  }
}

Benefits:

1. Now we can just add a decorator on the route handler (like in the example above) instead of following code to validate the request body.

try:
    dto = ProjectCreateDTO(request.get_json())
    dto.validate()
except DataError as e:
   return {"Error": str(e), "SubCode": "BAD_REQUEST"}

2. The error message will have more information like what and where the issue occured
3. This approach improves code organization, promotes code reuse, and enhances readability.

NOTE: This decorator must me only used after decorator token_auth.login_required if both decorator are to be used.

@token_auth.login_required
@validate_request(ProjectCreateDTO)
def post():
validated_dto = request.validated_dto 

[eternaltyro]

Just need some context to understand the change.

[d-rita]

Given that this will give more context for validation errors, LGTM

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

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[Aadesh-Baral]

@d-rita @eternaltyro I modified the decorator, so it now validates the DTO class using all of the path, query, and body parameters rather than just the body parameters. Could you kindly re-review the PR? The decorator is now more broadly applicable and may be used on views that takes path and query params. Take a look at the commit message for further details.

I apologize for making changes after the review.