This adds a flag to the DERP server which specifies to verify clients through a local
tailscaled. It is opt-in, so should not affect existing clients, and is mainly intended for
users who want to run their own DERP servers. It assumes there is a local tailscaled running and
will attempt to hit it for peer status information.
Updates #1264
Signed-off-by: julianknodt <julianknodt@gmail.com>