Implement user groups

[z9r5]

Loghouse has simple user permissions. User can be granted to access to a namespace and can be an admin (is_admin flag).
However, namespaces belong to teams, so more fine permission system is needed. Users and namespaces can be divided by groups where each group will have separate ClickHouse database with individual rotation and resource limits. Namespace will have an annotation — for example, group.loghouse.io=”xxx,yyy,zzz” label will mean logs from this namespace should be saved to 3 groups.

[may-cat]

Thanks for your issue. We are very busy right now.
New features will be planned after a few month, but your pull requests are always welcome.