Create additional iframe APIs to livechat

[sampaiodiego]

Description:

It would be good to have additional APIs to communicate with livechat iframe.

Server Setup Information:

• Version of Rocket.Chat Server: 0.64.2
• Operating System: any
• Deployment Method(snap/docker/tar/etc): any
• Number of Running Instances: any
• DB Replicaset Oplog: any
• Node Version: any
• mongoDB Version: any

Expected behavior:

I'm proposing the creation of the following additional functions:

• Set visitor token
• Set visitor name
• Set visitor email

This way an website using livechat can identify the visitor even before he have interacted with the page.

The functions should be available just like the setDepartment - docs

[hlehmann]

In case setGuestToken or setGuestEmail is use, it could be useful to let the visitor start/continue a conversation even when agents are offline.

A mail could be sent to the guest if the agent respond when the guest is offline.