added admin routes

[Uttkarsh24]

This pull request introduces significant changes to the backend of the application, primarily focusing on the management of tournaments, including creation, editing, deletion, and result handling. The changes also include the addition of new routes and controllers for admin functionalities.

New routes and controllers:

• Backend/src/app.js: Added a new admin route and imported adminRouter to handle admin-specific requests.
• Backend/src/routes/admin.routes.js: Created new routes for admin functionalities such as creating, editing, and deleting tournaments, as well as managing IDP and tournament results.
• Backend/src/controllers/admin.controller.js: Implemented new controller functions for handling tournament creation, editing, deletion, IDP management, and result posting/editing.

Model updates:

• Backend/src/models/idp.models.js: Added a new IDP model to store information about IDP associated with tournaments.
• Backend/src/models/result.models.js: Updated the Result model to include validation checks and ensure that players are registered in the tournament before adding results. [1] [2] [3]
• Backend/src/models/tournament.models.js: Added a reference to the IDP model in the Tournament schema.

Refactoring and cleanup:

• Backend/src/controllers/tournament.controller.js: Removed admin-controlled routes and functions, which are now handled by the new admin controller. [1] [2]
• Backend/src/routes/tournament.routes.js: Removed admin-specific routes and cleaned up the file to focus on user-accessible routes.