Events API improvements

[Sachavskyi]

I started usnig HS Events API in my project and identified a few improvements that would be very helpful:

1. Complete event types in API responses
   The endpoints GET /events/v3/events/event-types and GET /events/v3/events do not return all event types. For example, events like “Lifecycle change” or “Segment membership” are missing. It would be useful to have access to all event types available in the UI (see screenshots).
   
   

1. Full event definitions
   The endpoint GET /events/v3/event-definitions currently returns only custom event definitions. It would be great to include definitions for all events, not just custom ones.

2. Return event ID on creation
   The endpoint POST /events/v3/send does not return an event ID upon successful creation. It would be helpful if the response included the event ID.
   

   

3. Ability to delete events via API
   It would be beneficial to have an endpoint that allows deletion of events through the API.