Allow hiding the user part of the device name or update based on current user

[andrewheberle]

When a RustDesk client is first added the device is named username@device_name however in an environment where different users may log onto a machine this information is no longer correct.

It may be possible to implement this in a few ways if it is useful:

• Show the device name the same as it is now
• Update the username based on the currently logged in user, with only the device name shown if no user is logged in
• Only show the device name
• Allow some configuration option to select the above...maybe via a Strategy?

I had originally added this as a discussion item in the rustdesk/rustdesk repo but this is probably a more appropriate location.

[rustdesk]

close and lock to favor #284 (comment)