This pull request introduces significant improvements to the ticket bot API and permission handling in the Rustmail project. The main focus is on adding user session and permission checks, optimizing permission lookups with caching, and improving the handling of scheduled ticket closures. These changes enhance security by ensuring only authorized users can view or interact with tickets, and improve performance by reducing redundant permission queries.

Authentication and Permission Checks:

• Added session-based authentication to the handle_tickets_bot endpoint, requiring a valid session_id cookie and verifying user permissions before returning ticket data. Only admins or users with the required category permissions can view tickets.
• Introduced filtering of ticket lists based on user permissions, so non-admins only see tickets they are allowed to view.

Permission Caching and Utilities:

• Added a new permissions_cache module using the moka crate for efficient, time-limited caching of admin status and category permissions, reducing redundant Discord API calls.
• Implemented utility functions to check if a user is an admin/owner and to fetch and cache user permissions for ticket categories, including logic to determine if a user can view a channel.

Ticket Closure Improvements:

• Added a format_duration helper to consistently format human-readable durations for ticket closures and warnings.
• Improved scheduled closure logic to warn users when replacing an existing scheduled closure, showing the remaining time in a user-friendly format.

Code Quality and Refactoring:

• Refactored SQL query handling for thread and message fetching to improve readability and maintainability.

Dependency Updates:

• Added the moka crate to Cargo.toml for caching support.

These changes collectively improve both the security and performance of the ticket bot API, providing a better user experience and more robust permission management.