Add links to children of SubGuideCards

closes #132

Co-authored-by: Anna Headley <hackartisan@users.noreply.github.com>

app/views/sub_guide_cards/show.html.erb

@@ -1,6 +1,11 @@
-<h1>SubGuideCards#show</h1>
-<p>Find me in app/views/sub_guide_cards/show.html.erb</p>
-<%= @sub_guide_card.heading %>
+<h2>SubGuide: <%= @sub_guide_card.heading %></h2>
+<% if @sub_guide_card.children.present? %>
+  <ul>
+    <% @sub_guide_card.children.each do |sub_guide| %>
+      <li> <%= link_to sub_guide.heading, sub_guide_card_path(sub_guide.id) %> </li>
+    <% end %>
+  </ul>
+<% end %>
 <% @card_images.each do |image| %>
   <%= image_tag(image.iiif_url) %>
 <% end %>

spec/system/subguide_cards_spec.rb

@@ -11,13 +11,18 @@
   end
 
   describe 'show page' do
-    it 'displays card images as links' do
+    it 'displays card images' do
       ci = CardImage.new
       ci.path = SubGuideCard.find(2).path
       ci.image_name = 'imagecat-disk1-0675-B1764-0000.0219.tif'
       ci.save
       visit '/sub_guide_cards/2'
       expect(page).to have_selector('img')
     end
+
+    it 'links to child SubGuideCards' do
+      visit '/sub_guide_cards/4'
+      expect(page).to have_link('(As author)')
+    end
   end
 end