3 template modifications needed to be re-worked to be compatible with XF 2.1 and XF 2.2. The affected template modifications were for forum_post_quick_thread, forum_post_thread, and thread_edit templates.
a new forum permission was added: View contact-only threads by others. This node permission, if set to No, members who are not a part of the thread starters selected contact list can not see the thread. The thread will not show up in what's new, latest posts, or other applicable areas. For those belonging to the contact list used in the thread, that thread will be included in what's new, latest threads and other applicable areas. Note, that with this permission set to No, the last post information will be replaced with 'Private'. Set to View others permission on upgrade/install (normally Yes)
Q. How do I make contacts only thread not viewable to those not in my contact list?
A. For the node in question, ensure the option Allow contact lists to be used in this forum is checked. Then for the Registered group and Unregistered / Unconfirmed group set View contact-only threads by others to No.
Note, that you do not need to make that forum a Contacts only forum. That is up to you.
fixed an undefined index error when saving an edited thread from the thread list page.
changed the minimum php version to 7.2.
changed the status' icon to use fa-id-card, to better represent contacts only.
changed the thread view icon to fa-id-card and the title and screen reader phrase to invited participants, to make the list of who can participate clearer.
removed two redundant phrases.
made style changes to the contacts overlay when choosing to start a conversation with members from a contact list.
Added an option to use the id-card fa-icon or the phrase plus minus contact for the add remove contact link when viewing a members profile.
contacts can now be added or removed from the members profile page and the member overlay. You may select to add or remove the member from any contact list.
added an option to clear contacts from the conversation recipients field and remove the contact list name from the conversation page title if the conversation starter decided to not use contacts from a contact list. This was added for convenience.
added an option to nodes to set a forum as a contact list only forum. Only members with a valid contact list can start threads in the contacts only forum. Only the thread starters contacts from the chosen list can reply to the thread.