feat: Ability to lock to single conversation (#5881)

Adds the ability to lock conversation to a single thread for Whatsapp and Sms Inboxes when using outbound messages.

demo: https://www.loom.com/share/c9e1e563c8914837a4139dfdd2503fef

fixes: #4975

Co-authored-by: Nithin David <1277421+nithindavid@users.noreply.github.com>

.rubocop.yml

@@ -16,7 +16,6 @@ Metrics/ClassLength:
     - 'app/models/message.rb'
     - 'app/builders/messages/facebook/message_builder.rb'
     - 'app/controllers/api/v1/accounts/contacts_controller.rb'
-    - 'app/controllers/api/v1/accounts/conversations_controller.rb'
     - 'app/listeners/action_cable_listener.rb'
     - 'app/models/conversation.rb'
 RSpec/ExampleLength: