Add non-prefixed polymorphic admin routes

These routes are solved in a different way because of an inconsistency:
we define `groups` and `budget_investments`; we should either use the
`budget_` prefix in all places or remove it everywhere.

We can now share code using `polymorphic_path` even with these models.

spec/routing/polymorphic_routes_spec.rb

@@ -50,6 +50,56 @@ describe "Polymorphic routes" do
   describe "admin_polymorphic_path" do
     include ActionDispatch::Routing::UrlFor
 
+    it "routes budget investments" do
+      budget = create(:budget)
+      investment = create(:budget_investment, budget: budget)
+
+      expect(admin_polymorphic_path(investment)).to eq(
+        admin_budget_budget_investment_path(budget, investment)
+      )
+    end
+
+    it "routes budget groups" do
+      budget = create(:budget)
+      group = create(:budget_group, budget: budget)
+
+      expect(admin_polymorphic_path(group)).to eq(admin_budget_group_path(budget, group))
+    end
+
+    it "routes budget headings" do
+      budget = create(:budget)
+      group = create(:budget_group, budget: budget)
+      heading = create(:budget_heading, group: group)
+
+      expect(admin_polymorphic_path(heading)).to eq(
+        admin_budget_group_heading_path(budget, group, heading)
+      )
+    end
+
+    it "routes poll booths" do
+      booth = create(:poll_booth)
+
+      expect(admin_polymorphic_path(booth)).to eq(admin_booth_path(booth))
+    end
+
+    it "routes poll officers" do
+      officer = create(:poll_officer)
+
+      expect(admin_polymorphic_path(officer)).to eq admin_officer_path(officer)
+    end
+
+    it "routes poll questions" do
+      question = create(:poll_question)
+
+      expect(admin_polymorphic_path(question)).to eq(admin_question_path(question))
+    end
+
+    it "routes poll answer videos" do
+      video = create(:poll_answer_video)
+
+      expect(admin_polymorphic_path(video)).to eq admin_video_path(video)
+    end
+
     it "routes milestones for resources with no hierarchy" do
       proposal = create(:proposal)
       milestone = create(:milestone, milestoneable: proposal)