Merge branch 'mk-add-chat-seats-logic' into 'master'

Implement checking for the add-on seat for chat users

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/142800



Merged-by: Jarka Košanová <jarka@gitlab.com>
Approved-by: Roger Woo <rwoo@gitlab.com>
Approved-by: David O'Regan <doregan@gitlab.com>
Approved-by: Jarka Košanová <jarka@gitlab.com>
Reviewed-by: Gosia Ksionek <mksionek@gitlab.com>
Reviewed-by: Nikola Milojevic <nmilojevic@gitlab.com>
Reviewed-by: Mehmet Emin INAC <minac@gitlab.com>
Reviewed-by: Torsten Linz <tlinz@gitlab.com>
Co-authored-by: Małgorzata Ksionek <mksionek@gitlab.com>