fix: validation and error display for due date extensions in the API

[efortish]

Fix validation and error display for due date extensions in the API

Description

This PR addresses the issue where the API did not correctly handle and display error cases where the due_datetime field was empty or incorrectly formatted; also, the API did not correctly handle the student/email field when it does not exist. Additionally, this PR ensures that the error messages returned by the API are clear and relevant to the actual validation error encountered.
This is the fix for this issue

Changes Made

• Reordered Validation Checks, moved the validation check for the student before the check of due_date to ensure that the student is validated first. This prevents misleading error messages when both fields are invalid.

Consistent Error Handling:

• Ensured that all validation errors are returned using JsonResponse with a clear error key. This makes the error messages consistent and easier for the frontend to handle.

Detailed Error Message:

• Added specific error message when due_datetime is empty or incorrectly formatted.
• Ensure that the error message is correct when the student/email doesnt exist.
• Ensured that the error message for invalid due_datetime is only returned if the student exist.

Objective

The objective of these changes was to improve the user experience by providing clear and accurate error messages when validation fails. This helps users understand what went wrong and how to correct their input.

Achievements

Improved User Feedback: Users now receive specific error messages for each validation issue, making it easier to correct their input.
Consistent Error Handling: All validation errors are handled consistently, making the API more robust and predictable.
Better Code Organization: The validation checks are now logically ordered, improving the readability and maintainability of the code.

Testing

Tested with various inputs to ensure that the correct error messages are returned for each validation failure.
Verified that the frontend correctly displays the error messages returned by the API.

How to test

In the lms, go to the Extensions section in the instructor dashboard and try different inputs, you can:

1. Leave all fields blank
2. Put an invalid student/email and the other fields filled out
3. Put an invalid student/email and other fields blank or some filled out
4. Put a valid student/email and other fields blank or some filled out
5. Put a valid student/email, valid graded subsection, but the due_datetime wrong

Note: Please keep in mind that the input "reason" is not required in the serializer, therefore it doesnt matter whether it is filled out or not

Screencast.from.2025-01-28.11-49-33.webm

Related Issues

PR #35392: https://github.com/openedx/edx-platform/pull/35392/files#diff-2e708ec7862cbe8e9fe138f4cde50b224d98e95f958dfc645b5ab76075035d8dR2994-R3008
Issue #124: Errors are not displayed correctly in extensions tab #124
Issue #422: [Test failure] TC_INSTRUCTOR_8: Errors are not displayed correctly in extensions tab #422

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[efortish]

Hello @mariajgrimaldi , could you help me with the review of this PR? I will also refine the issue with some things I found.

[BryanttV]

Hi @efortish! Thanks for your contribution. I was testing the changes and everything works fine! I only have a few minor comments.

• Remove the trailing spaces in the function. I recommend using trailing spaces extension in VSCode.
• Remove the double line break in the function.

As a suggestion, It's possible to add a margin in the error message?