Assign Nodes to Roles

### Discussed in https://github.com/pelican-dev/panel/discussions/21

<div type='discussions-op-text'>

<sup>Originally posted by **Oldbear200** April 12, 2024</sup>
Hey please add that admins can assign a node to a user so he can create / manage / delete services with just that node.
Would love that</div>

Scope roles to specific nodes. (many to many)