feat : add event recommendation system

[Chesblaw]

Description
A prototype recommendation engine suggests events based on past user purchases. It uses a straightforward collaborative filtering approach.

A new FastAPI endpoint, /recommend-events, has been added. This includes the relevant request and response models, as well as test cases.

Changes made
Added a mocked dataset called mock_user_events that shows users and their purchased events.

Implemented a collaborative filtering algorithm.

This algorithm finds similar users based on event overlap.

It recommends up to three events that the current user has not yet attended.

Created a new endpoint:

POST /recommend-events

Request: {"user_id": ""}

Response: {"recommendations": ["event1", "event2", ...]}

Added error handling.

It returns a 404 error with a JSON body if the user is not found.

Added unit tests in tests/test_recommend.py.

[BigBen-7]

@Chesblaw resolve conflicts

[Chesblaw]

Hey@BigBen-7 i think someone merged it