Add API for course allocation and enhance allocation logic

[vikrantwiz02]

This pull request introduces improvements to the course allocation process, focusing on data integrity and user control during allocation. The key changes add validation to ensure all registered courses are properly linked to their slots, allow skipping problematic courses, and provide an API for admins to quickly fix missing course-slot associations.

Enhancements to course allocation and slot validation:

• Added a new validation step (validate_course_slots) before allocation begins to ensure all registered courses are present in their respective course slots. If any are missing, the allocation is halted and a detailed list of issues is returned to the client. [1] [2]
• Updated the allocation process and random_algo to support skipping specific courses (by course_id) during allocation. Skipped courses are not allocated, and the response includes details about skipped courses and affected students. [1] [2] [3] [4]

New administrative API endpoint:

• Introduced the add_course_to_slots_api endpoint, allowing academic admins to add a course to multiple course slots in bulk, addressing missing associations flagged by validation. [1] [2]

API and codebase improvements:

• Enhanced error handling and input validation for new parameters (e.g., skip_course_ids, slot_ids) in the relevant API endpoints. [1] [2]
• Refactored imports to support new functionality, such as atomic transactions.

These changes improve the reliability of course allocation, provide better diagnostics for admins, and introduce tools to quickly resolve data inconsistencies.