2.4. Make a POST endpoint inside a new controller that allows a logged in user to attend a new event.

[SivTheBearBoy]

• The JSON body to submit an attendance should contain a user id and an event id.
• Endpoint returns the event that the user has attended.
• Endpoint is responsible to check the availability of the event based on the date and start time.
  • If the above condition fails, the endpoint needs to provide an error message of what went wrong.
• Inside the same controller, there should be a GET endpoint that allows a logged-in user to view the list of attendees.
• The controller can delete events that the user attended, in case the user cannot attend the event anymore.