db: add sqlite "source of truth" schema

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

cmd/headscale/cli/serve.go

@@ -2,10 +2,12 @@ package cli
 
 import (
 	"errors"
+	"fmt"
 	"net/http"
 
 	"github.com/rs/zerolog/log"
 	"github.com/spf13/cobra"
+	"github.com/tailscale/squibble"
 )
 
 func init() {
@@ -21,6 +23,12 @@ var serveCmd = &cobra.Command{
 	Run: func(cmd *cobra.Command, args []string) {
 		app, err := newHeadscaleServerWithConfig()
 		if err != nil {
+			var squibbleErr squibble.ValidationError
+			if errors.As(err, &squibbleErr) {
+				fmt.Printf("SQLite schema failed to validate:\n")
+				fmt.Println(squibbleErr.Diff)
+			}
+
 			log.Fatal().Caller().Err(err).Msg("Error initializing")
 		}