Define many-to-many table to represent relations between user scope (project or individual user) and container registry

[kyujin-cho]

After #1907 is resolved, we can create a new table to define relations between user/project and container registry.

• Every users should be capable of having container registry dedicated to itself.
• Same rule applies to project, and in this case every users residing in that project can benefit from such registries.
• A user or project can be assigned multiple registries at once.
• Multiple users or projects should be able to point at same container registry at once.