New admin page for invitations

app/views/admin/invitations/index.html.erb

@@ -0,0 +1,25 @@
+<section>
+  <h2>Invitations</h2>
+
+  <% if @invitations_used.any? %>
+    <h3>Accepted (<%= @invitations_used.length %>)</h3>
+    <table>
+      <thead>
+        <tr>
+          <th>Token</th>
+          <th>Accepted</th>
+          <th>Invited user</th>
+        </tr>
+      </thead>
+      <tbody>
+        <% @invitations_used.each do |invitation| %>
+          <tr>
+            <td class="overflow-ellipsis"><%= invitation.token %></td>
+            <td><%= invitation.used_at.strftime("%Y-%m-%d") %></td>
+            <td><%= User.find(invitation.invited_user_id).address %></td>
+          </tr>
+        <% end %>
+      </tbody>
+    </table>
+  <% end %>
+</section>

app/views/shared/_admin_nav.html.erb

@@ -5,6 +5,10 @@
         <%= link_to "Dashboard", admin_root_path,
              class: @current_section == :dashboard ? "active" : nil %>
       </li>
+      <li>
+        <%= link_to "Invitations", admin_invitations_path,
+              class: @current_section == :invitations ? "active" : nil %>
+      </li>
       <li>
         <%= link_to "Donations", admin_donations_path,
               class: @current_section == :donations ? "active" : nil %>