Use rights for ponos farms

We want to control who has access to all ponos agents (through their farms).

By default, a user has NO access to any farm, there is no "public" ponos farm (unlike Corpus or ML Models for example).

There is NO endpoints to create the rights for a group or user on a farm: it will only be managed through the admin interface.

To summarize:

all these rights have the same level: 10. There is no management, simply access to the farm and its agents.
the following ponos endpoints now need to check if the current user has any right to use the farm:
- ListFarms
- ListAgents
All endpoints that create a process must check that the user has access to the requested farm (or any farm at all)
the ponos farm admin details must list all current rights (both at user & group level), and allow an admin to create one