Evidently, wireguard's (use of) fwmark is not well understood. In short,
it determines which routing table to use for a tunnel's packets.
Adding a fwmark to a roadwarrior client config won't do anything to the
actual packets sent to a peer: Packets do not get marked.
A QRCode with `FwMark = ...` in it is invalid.
FwMark is now excluded from client configs (but is written to the
server config /etc/wireguard/wgX.conf).
Potential breaking change of `WGUI_FORWARD_MARK` to `WGUI_FIREWALL_MARK`
But this has the effect of making users eventually notice that it
probably does not do what they want/think.
See:
https://ro-che.info/articles/2021-02-27-linux-routinghttps://casavant.org/2020/10/10/wireguard-fwmark.htmlhttps://www.blinkenlights.ch/ccms/posts/source-based-routing/
