Club Entities

[rosscado]

Separate the club entity from the POST event request, since we won't be recreating clubs on every event.
This will then require a means of looking up the club and linking the event to it.
E.g.

club:
   id: Lucan Cycling Road Club
...
event:
   organised_by:
     club_id: Lucan Cycling Road Club

Or
club_id = GET /api/clubs/?title=Lucan Cycling Road Club

event:
   organised_by:
     club_id: {club_id}

Originally posted by @rosscado in #57 (comment)