Handling the following issues: Adding custom classes to block to allow for dynamic ajax Adding private_message_thread cache context Adding private message actions block, removing 'create thread' from header of thread page Removing create link altogether. Handled by block now Issue #2952860 by opdavies, Jaypan: Emails not being sent when messages are queued Issue #2962872 by Jaypan: Static calls in PrivateMessageThreadMemberWidget need to be converted to dependency injection Issue #2962096: Unable to install Private Message due to unmet dependencies: block.block.actions (bartik)