Checks a policy as a write would, without storing it. As on Tailscale,
a refused policy answers 200 with its reason; only an empty body is 400.
Terraform provider 0.29.3 calls it at plan time.
Backs the tailscale_user and tailscale_users data sources. getUser maps
gorm/ErrUserNotFound to 404; unmodelled fields are honest constants,
deviceCount/lastSeen/currentlyConnected aggregate the user's nodes.
Add the v2 foundation — Basic/Bearer auth, scope scaffolding, the
tailnet check, and the Tailscale error shape — plus the auth-key
endpoints mapped onto Headscale pre-auth keys.
Kristoffer Dalby
MsfPablo