Add PUT /v3/apps/:guid/processes to associate a process with an app

 - Refactor ProcessesController to call to ProcessesHandler, which is
 responsible for dealing with request bodies and raising the appropriate
 API errors when necessary.
 - New AppRepository to handle interactions with apps_v3

[#79386466]
remove process_repository dependency from app_repository
use existing dependency injection pattern in appv3 controller
Refactor ProcessHandler to move most of the api logic out

[#79386466]
wip - optimize sql query