Limit how many devices users are permitted to have

[SkullKill]

Is your feature request related to a problem? Please describe.
Admins have no control on what device, and how many devices the user deploy the vpn clients to.

Describe the solution you'd like
We would like to have the option to disable the option for the user to provision their own VPN (both defguard and native wireguard).

So , an option to completely disable the "Add a new device" option for users. And only allow the Admins to generate a token for the user to use to provision their defguard clients.

[teon]

Related to: #609

[teon]

Done - releasing in 1.0