Simple addon that will allow you to give your usergroups the permissions to lock conversations or allow them to use the allow anyone to invite others option. This is for xF2.1 and above.
Fixed Error: ErrorException: Fatal Error: Class Snog\ConvoLockInvite\Setup contains 3 abstract methods and must therefore be declared abstract or implement the remaining methods
With permissions both set to NO for the primary user group (Registered Users) and both set to YES for the secondary user groups (Mods and Admins), I no longer get the option to unlock a Conversation when I click edit. I only get the option to edit the thread title and "Allow anyone in the conversation to invite others".
With the add-on disabled, I'll get the option to Lock/Unlock the conversation.