Convert db backend to use Gorm, with basis for support

for Mysql and Postgres in addition to existing Sqlite

backend/internal/api/middleware/auth.go

@@ -48,7 +48,7 @@ func Enforce(permission string) func(http.Handler) http.Handler {
 					return
 				}
 
-				userID := int(claims["uid"].(float64))
+				userID := uint(claims["uid"].(float64))
 				_, enabled := user.IsEnabled(userID)
 				if token == nil || !token.Valid || !enabled {
 					h.ResultErrorJSON(w, r, http.StatusUnauthorized, "Unauthorised", nil)