Optimization of sms and group chat features.
Addressed the following tickets:
RS-5621: Improved external session creation behavior. If there is an existing session with an external number (used trunk with stickiness), upon an attempt to create a chat with the same number an existing session will open. If a message was sent from a non-stickiness trunk in an external chat session (not a group), a chat will transform into a group chat. External group chat (non-stickiness trunk) can’t select from or to which number to send a message.