_authelia_scope_access previously derived a throwaway "<service>-only" group
every time it ran, so scoping two different sites to the same set of people
meant either duplicating membership by hand or hitting a false "already
scoped" early-return that silently skipped adding the second site's own
rule. Now it offers existing groups by number (any site can join one), lets
a new name be typed freely (e.g. "customer1"), and the already-scoped check
is keyed to the (domain, group) pair instead of the group name alone.
Reframes the access question as native (default, unrestricted) vs. outside
access (a named group) per the AD-style users/groups mental model, and adds
menu option 14 to rename an existing group everywhere it's referenced
(access_control.rules subjects + every member's users.yml entry). The
"-only" suffix stays internal only — every other function that already
keys off it (reporting, per-user group toggle, unprotect cleanup) is
untouched.