The SimpleX sender allowlist (SIMPLEX_ALLOWED_USERS) previously matched
against both the stable numeric contactId (user_id) and the mutable
display name (user_name). Since any SimpleX contact can change their
localDisplayName / profile.displayName to match another user's, this
allowed an unauthorized contact to bypass the allowlist by setting a
colliding display name.
Remove the user_name check so that SIMPLEX_ALLOWED_USERS only matches
on the immutable contactId. Operators must use numeric contact IDs in
the allowlist.
Fixes#44729
(cherry picked from commit b4aa29da1567d45920f79aabdb36b44c5f87bde5)
4670467534