feat: Chat operator to communicate with guest user

[shariquerik]

We used to have this feature in the older version of the chat app.

Added Chat operators table multi-select field in chat settings Now messages from the guest users will only be visible to the users mentioned in the chat operators field. Also added users table multi-select field in Chat Room doctype.

In Chat Settings [email protected] is the chat operator. And you can see he is able to see the John Doe Guest User's message

Jane Doe is a company user and she can only see a direct message from the company user

Guest User

We already have a members field in Chat Room which stores the user's name as a comma separate value. Need suggestion should we use a text field or a multi-select field for this? I think multi-select should be the obvious choice but why it was implemented as a text field? Security reasons?