switched setPreference to handleJSONResponse & moved error message to the server

Author: Oaphi

app/assets/javascripts/qpixel_api.js

@@ -238,13 +238,9 @@ window.QPixel = {
 
     const data = await resp.json();
 
-    if (data.status !== 'success') {
-      console.error(`Preference persist failed (${name})`);
-      console.error(resp);
-    }
-    else {
+    QPixel.handleJSONResponse(data, (data) => {
       QPixel._updatePreferencesLocally(data.preferences);
-    }
+    });
   },
 
   filters: async () => {

app/controllers/users_controller.rb

@@ -198,6 +198,7 @@ def set_preference
                      preferences: current_user.preferences }
     else
       render json: { status: 'failed',
+                     message: 'Failed to save the preference',
                      errors: ['Both name and value parameters are required'] },
              status: 400
     end