Context:
In the course of the collection scope feature a new endpoint is required that allows to query for available definitions available to be set as collection scope.

AT:

• new endpoints are available `GET /api/definition/*` that allow to query for available definitions (process & decision) & tenants combinations
  • get a definition by type and key `GET /api/definition/:type/:key` along with available tenants (based on current user auth)
  • list definitions (key & type) `GET /api/definition` along with available tenants (based on current user auth)
  • list definitions grouped by tenant `GET /api/definition/_groupByTenant`, only return authorized tenants and tenant & definition combinations
• the new endpoints are documented