Create API endpoint to receive events

[VictorPeralta]

Clients will create new events by POSTing to the /events endpoint with event data and API_KEY

The steps the backend takes in this endpoint are:

1. Validate request
2. Get project associated to provided API key
3. Check if a event group with the event's stack trace and title exists. If it does not, create event group.
4. Insert event into DB, with a reference to the event group.

Sequence Diagram