feat(app): disable API when demo mode is enabled

app/apps/api/permissions.py

@@ -0,0 +1,10 @@
+from rest_framework.permissions import BasePermission
+from django.conf import settings
+
+
+class NotInDemoMode(BasePermission):
+    def has_permission(self, request, view):
+        if settings.DEMO and not request.user.is_superuser:
+            return False
+        else:
+            return True