Configure LAN access for individual clients

[schox-nor]

Background
Some users need LAN access, others, who only use the VPN to secure data on WIFI, secure mobile data or avoid geo-blocking when travelling, etc might not
Typical - give friends access to a pivpn user, without giving access to the LAN

Solution suggestion
The (one?) technical solution is outlined in support request #1244
#1244 (comment)

As this might be an optional feature, the configuring of the user might be done in the "same" way as "pivpn -qr" - list users and ask for client number to configure, show status and change/toggle access. - eg. "pivpn -lan" (change LAN access for clients)

The current solution works great, but nicer to have it "automated".

There might be downsides and limitations I'm not aware of, but appreciate if this is considered.