feat/add-requirement-api

[Duy-Nguyen1104]

Description

This PR is built on top of feat/template-coursemap-api-updated. Please review that PR first.

This pull request introduces the Requirement feature to the CourseFlow API, as I noticed that a requirement entity is not created based on this doc requirement: https://thoth-tech.netlify.app/products/courseflow/documentation/design/backend-functional-requirements/#requirements.
It adds a new Requirement model, migration, and API routes for creating, retrieving, updating, and deleting requirements.
Relevant tests have also been created or updated to ensure the correctness of the new endpoints and model logic.

Type of change

• [x ] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Added and ran unit tests for the new Requirement model and API endpoints.
• Checked that all existing and new tests pass locally
• Verified API routes using automated request specs and manual testing via Postman
• Confirmed database migration applies cleanly and schema is updated.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation if appropriate
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works