Simplify goreleaser, package deb and rpm

This commit simplifies the goreleaser configuration and then adds nfpm
support which allows us to build .deb and .rpm for each of the ARCH we
support.

The deb and rpm packages adds systemd services and users, creates
directories etc and should in general give the user a working
environment. We should be able to remove a lot of the complicated,
PEBCAK inducing documentation after this.

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

docs/packaging/headscale.systemd.service

@@ -0,0 +1,52 @@
+[Unit]
+After=syslog.target
+After=network.target
+Description=headscale coordination server for Tailscale
+X-Restart-Triggers=/etc/headscale/config.yaml
+
+[Service]
+Type=simple
+User=headscale
+Group=headscale
+ExecStart=/usr/bin/headscale serve
+Restart=always
+RestartSec=5
+
+WorkingDirectory=/var/lib/headscale
+ReadWritePaths=/var/lib/headscale /var/run
+
+AmbientCapabilities=CAP_NET_BIND_SERVICE CAP_CHOWN
+CapabilityBoundingSet=CAP_CHOWN
+LockPersonality=true
+NoNewPrivileges=true
+PrivateDevices=true
+PrivateMounts=true
+PrivateTmp=true
+ProcSubset=pid
+ProtectClock=true
+ProtectControlGroups=true
+ProtectHome=true
+ProtectHome=yes
+ProtectHostname=true
+ProtectKernelLogs=true
+ProtectKernelModules=true
+ProtectKernelTunables=true
+ProtectProc=invisible
+ProtectSystem=strict
+RemoveIPC=true
+RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
+RestrictNamespaces=true
+RestrictRealtime=true
+RestrictSUIDSGID=true
+RuntimeDirectory=headscale
+RuntimeDirectoryMode=0750
+StateDirectory=headscale
+StateDirectoryMode=0750
+SystemCallArchitectures=native
+SystemCallFilter=@chown
+SystemCallFilter=@system-service
+SystemCallFilter=~@privileged
+UMask=0077
+
+[Install]
+WantedBy=multi-user.target