Fix flagging/unflagging in the admin section

We weren't adding the HTML id our JavaScript expects, and so the page
didn't update the flag element.

app/views/admin/debates/show.html.erb

@@ -2,7 +2,7 @@
   <%= t("admin.header.title") %> - <%= t("admin.menu.debates") %> - <%= @debate.title %>
 <% end %>
 
-<div class="debate-show">
+<div id="<%= dom_id(@debate) %>" class="debate-show">
   <h2><%= @debate.title %></h2>
 
   <% if @debate.conflictive? %>

spec/shared/system/flaggable.rb

@@ -1,12 +1,21 @@
-shared_examples "flaggable" do |factory_name|
+shared_examples "flaggable" do |factory_name, admin: false|
   include ActionView::RecordIdentifier
 
-  let(:user) { create(:user, :level_two) }
   let(:flaggable) { create(factory_name) }
 
+  let(:user) do
+    if admin
+      create(:administrator).user
+    else
+      create(:user, :level_two)
+    end
+  end
+
   let(:path) do
     if flaggable.is_a?(Comment)
       polymorphic_path(flaggable.commentable)
+    elsif admin
+      admin_polymorphic_path(flaggable)
     else
       polymorphic_path(flaggable)
     end

spec/system/admin/debates_spec.rb

@@ -6,6 +6,8 @@ describe "Admin debates" do
     login_as(admin.user)
   end
 
+  it_behaves_like "flaggable", :debate, admin: true
+
   scenario "Index" do
     create(:debate, title: "Best beaches")