Issue 105 | Feature: Implemented detailed Availability data model

[Flapjacck]

This pull request introduces significant improvements to the availability API, focusing on validation, conflict checking, and enhanced scheduling features. The changes include robust request validation using Zod schemas, stricter permission checks, support for recurring and team-based availabilities, and a new endpoint for finding overlapping availability between users. Additionally, the rrule library is added for potential recurrence handling.

Validation and API Improvements

• Added Zod schemas for request validation to the availability routes, ensuring data integrity and clear error messaging for creation and update operations (backend/src/routes/availabilityRoutes.ts).
• Implemented detailed validation and conflict checking for creating and updating availabilities, including team access verification and overlap detection (backend/src/routes/availabilityRoutes.ts). [1] [2]

Scheduling and Matching Features

• Enhanced the /matches endpoint to support finding overlapping availability between specific users or all team members, with support for minimum duration filtering and detailed match results (backend/src/routes/availabilityRoutes.ts).

Team Availability Enhancements

• Improved the team availability endpoint to support querying within a date range and optional filtering by availability type (backend/src/routes/availabilityRoutes.ts).

Dependency Updates

• Added the rrule package and its dependency tslib to package.json and pnpm-lock.yaml for future support of recurrence rules (backend/package.json, backend/pnpm-lock.yaml). [1] [2] [3] [4] [5] [6]

Closes #105