Move admin/pubsubhubbub controller to admin/subscriptions (#3442)

app/views/admin/subscriptions/_subscription.html.haml

@@ -0,0 +1,16 @@
+%tr
+  %td
+    %samp= subscription.account.acct
+  %td
+    %samp= subscription.callback_url
+  %td
+    - if subscription.confirmed?
+      %i.fa.fa-check
+  %td{ style: "color: #{subscription.expired? ? 'red' : 'inherit'};" }
+    = precede subscription.expired? ? '-' : '' do
+      = time_ago_in_words(subscription.expires_at)
+  %td
+    - if subscription.last_successful_delivery_at?
+      = l subscription.last_successful_delivery_at
+    - else
+      %i.fa.fa-times

app/views/admin/subscriptions/index.html.haml

@@ -0,0 +1,15 @@
+- content_for :page_title do
+  = t('admin.subscriptions.title')
+
+%table.table
+  %thead
+    %tr
+      %th= t('admin.subscriptions.topic')
+      %th= t('admin.subscriptions.callback_url')
+      %th= t('admin.subscriptions.confirmed')
+      %th= t('admin.subscriptions.expires_in')
+      %th= t('admin.subscriptions.last_delivery')
+  %tbody
+    = render @subscriptions
+
+= paginate @subscriptions