Allow use of mac-specific shortcuts for copy/paste in RDP (Cmd+V/C/Z)

Presently, from a mac system, regardless of browser, copy/paste functionality only works with the Windows specific keys using RDP. This is expected, and as described in a similar issue in Guacamole-1386, it's because Guacamole simply sends the keys to the OS.

However, I would like to request/wish that Guacamole could perhaps detect Mac based browser clients and allow the mac copy/paste keys to work over RDP the same as Ctrl+v/z/c. The current Mac RDP client from Microsoft implements this behavior, and it is great for sanity when copying/pasting multiple things between the host OS and Guacamole session.

To my mind, this would be similar to Guacamole-1804 .