Format validation errors as human readable messages

app/controllers/groups/variables_controller.rb

@@ -7,7 +7,7 @@ module Groups
         format.json do
           return head :ok if @group.update(variables_params)
 
-          render status: :bad_request, json: @group.errors.to_hash
+          render status: :bad_request, json: @group.errors.full_messages
         end
       end
     end

app/controllers/projects/variables_controller.rb

@@ -6,7 +6,7 @@ class Projects::VariablesController < Projects::ApplicationController
       format.json do
         return head :ok if @project.update(variables_params)
 
-        render status: :bad_request, json: @project.errors.to_hash
+        render status: :bad_request, json: @project.errors.full_messages
       end
     end
   end