Copilot/add course waitlist feature

[kavyashri-as]

This pull request introduces a comprehensive waitlist feature to the course registration system. It adds new API endpoints, DTOs, service interfaces, and mappings to support waitlist operations, including joining, leaving, updating, clearing, notifying, and reordering waitlists for courses. The changes also expand course DTOs to include waitlist-related information, and register the required services and repositories for dependency injection.

Waitlist Feature Implementation:

• Added a new WaitlistController with endpoints for managing waitlist entries, including joining, leaving, updating, clearing, notifying, and reordering waitlists for courses.
• Introduced DTOs for waitlist operations: CreateWaitlistEntryDto, WaitlistEntryDto, and UpdateWaitlistEntryDto.
• Created the IWaitlistService interface to define waitlist-related business logic and operations.
• Registered IWaitlistService, IWaitlistRepository, and related notification services for dependency injection in Program.cs.
• Added mapping profiles for waitlist DTOs and entities, enabling transformation between domain models and API responses.

Course DTO Enhancements:

• Extended CourseDto, CreateCourseDto, and UpdateCourseDto to include MaxEnrollment, IsFull, and WaitlistCount properties, providing more visibility into course capacity and waitlist status. [1] [2] [3]
• Updated mapping logic to populate new course DTO properties from the domain model, including calculation of IsFull and WaitlistCount.

Notification Service Integration:

• Added the INotificationService interface to abstract notification logic for waitlist events, supporting email and in-app notifications.
• Registered the notification service for dependency injection in Program.cs.

Domain Model Mapping Updates:

• Updated entity-to-DTO mapping profiles to include waitlist relationships for students and courses, ensuring proper data transformation and integrity. [1] [2]

These changes collectively enable robust waitlist management within the course registration API, supporting both student and administrative operations.