Extract documents action from Answer controller

This way we have a controller just to manage
Poll::Question::Answer related documents in the
same way we have for videos and images.

app/components/admin/poll/questions/answers/documents/index_component.html.erb

@@ -0,0 +1,52 @@
+<%= back_link_to %>
+
+<h2><%= t("admin.questions.show.answers.documents_list") %></h2>
+
+<ul class="breadcrumbs">
+  <li><%= answer.question.title %></li>
+  <li><%= answer.title %></li>
+</ul>
+
+<div class="poll-question-form">
+  <%= form_for(Poll::Question::Answer.new, url: admin_answer_documents_path(answer)) do |f| %>
+    <%= render "shared/errors", resource: answer %>
+
+    <div class="documents">
+      <%= render "documents/nested_documents", f: f %>
+    </div>
+
+    <div class="small-12 medium-6 large-2">
+      <%= f.submit(class: "button expanded", value: t("shared.save")) %>
+    </div>
+  <% end %>
+
+  <% if answer.documents.present? %>
+    <table>
+      <tr>
+        <th scope="col"><%= t("admin.questions.show.answers.document_title") %></th>
+        <th scope="col"><%= t("admin.questions.show.answers.document_actions") %></th>
+      </tr>
+
+      <% answer.documents.each do |document| %>
+        <tr>
+          <td>
+            <%= link_to document.title, document.attachment %>
+          </td>
+          <td>
+            <%= render Admin::TableActionsComponent.new(document,
+              actions: [:destroy],
+              destroy_path: document_path(document)
+            ) do |actions| %>
+              <%= actions.action(:download,
+                                 text: t("documents.buttons.download_document"),
+                                 path: document.attachment,
+                                 target: "_blank",
+                                 rel: "nofollow") %>
+
+            <% end %>
+          </td>
+        </tr>
+      <% end %>
+    </table>
+  <% end %>
+</div>

app/components/admin/poll/questions/answers/documents/index_component.rb

@@ -0,0 +1,7 @@
+class Admin::Poll::Questions::Answers::Documents::IndexComponent < ApplicationComponent
+  attr_reader :answer
+
+  def initialize(answer)
+    @answer = answer
+  end
+end