Service and Plan events user broker as the actor instead of the user

[#83975716]
[#83975698]
Unify events_repository methods
Rename binding => service_binding
Some more refactoring of the EventRepository

The goal here is for all methods with similar names (create_X_event) to have similar interfaces (in this case, with type, object, and request_params as the three args).

The create_event helper method is also different. It has more arguments
so that the purpose of each one is clear (we were previously overloading some arguments, like actee).
Update events api spec to include changes to the actor field

[finishes #83975716]
[finishes #83975698]