Add displaying no_milestones text on admin

app/models/interest.rb

@@ -0,0 +1,5 @@
+class Interest < ActiveRecord::Base
+  belongs_to :user
+  belongs_to :interestable, polymorphic: true
+  
+end

app/views/admin/budget_investments/_milestones.html.erb

@@ -29,4 +29,8 @@
       <% end %>
     </tbody>
   </table>
+<% else %>
+  <p>
+    <%= t('admin.milestones.index.no_milestones') %>
+  </p>
 <% end %>

config/locales/admin.en.yml

@@ -169,6 +169,7 @@ en:
         table_description: "Description"
         table_actions: "Actions"
         delete: "Delete milestone"
+        no_milestones: "Don't have defined milestones"
       new:
         creating: Create milestone
       edit:

config/locales/admin.es.yml

@@ -169,6 +169,7 @@ es:
         table_description: "Descripción"
         table_actions: "Acciones"
         delete: "Eliminar hito"
+        no_milestones: "No hay hitos definidos"
       new:
         creating: Crear hito
       edit:

spec/features/admin/budget_investment_milestones_spec.rb

@@ -19,6 +19,13 @@ feature 'Admin budget investment milestones' do
       expect(page).to have_content(milestone.title)
       expect(page).to have_content(milestone.id)
     end
+
+    scenario 'Displaying no_milestones text' do
+      visit admin_budget_budget_investment_path(@investment.budget, @investment)
+
+      expect(page).to have_content("Milestone")
+      expect(page).to have_content("Don't have defined milestones")
+    end
   end
 
   context "New" do