Provide background color when first checking API session

tailbone/api/auth.py

@@ -57,7 +57,16 @@ class AuthenticationView(APIView):
         if self.request.user:
             data = self.user_info(self.request.user)
             data['user']['is_root'] = self.request.is_root
+
         data['permissions'] = list(self.request.tailbone_cached_permissions)
+
+        # background color may be set per-request, by some apps
+        if hasattr(self.request, 'background_color') and self.request.background_color:
+            data['background_color'] = self.request.background_color
+        else: # otherwise we use the one from config
+            data['background_color'] = self.rattail_config.get(
+                'tailbone', 'background_color')
+
         return data
 
     @api