Fix timestamps for certain activity types

lib/clacks_web/templates/frontend/_action_status.html.eex

@@ -11,7 +11,7 @@
       <%= past_tense %> by <a href="<%= local_actor_link(@action_actor) %>"><%= @action_actor.data["preferredUsername"] %></a>
     </p>
     <p class="status-meta-right">
-    <time datetime="<%= @action_activity.data["published"] %>"><%= display_timestamp(@action_activity.data["published"]) %></time>
+    <time datetime="<%= iso_datetime(@action_activity) %>"><%= display_timestamp(@action_activity) %></time>
     </p>
   </div>
   <div class="status-meta">
@@ -26,7 +26,7 @@
       </a>
     </h3>
     <p class="status-meta-right">
-      <time datetime="<%= @original_note["published"] %>"><%= display_timestamp(@original_note["published"]) %></time>
+      <time datetime="<%= iso_datetime(@original_activity) %>"><%= display_timestamp(@original_activity) %></time>
       <a href="<%= @original_note["url"] || @original_note["id"] %>" class="status-permalink">Permalink</a>
     </p>
   </div>

lib/clacks_web/templates/frontend/_follow_notification.html.eex

@@ -4,7 +4,7 @@
       Followed by <a href="<%= local_actor_link(@actor) %>"><%= @actor.data["preferredUsername"] %></a>
     </p>
     <p class="notification-info-right">
-      <time datetime="<%= @activity.data["published"] %>"><%= display_timestamp(@activity) %></time>
+      <time datetime="<%= iso_datetime(@activity) %>"><%= display_timestamp(@activity) %></time>
     </p>
   </div>
 </div>

lib/clacks_web/templates/frontend/_status.html.eex

@@ -13,7 +13,7 @@
       </h3>
     </div>
     <p class="status-meta-right">
-      <time datetime="<%= @note["published"] %>" class="dt-published"><%= display_timestamp(@note["published"]) %></time>
+    <time datetime="<%= iso_datetime(@note["published"]) %>" class="dt-published"><%= display_timestamp(@note["published"]) %></time>
       <a href="<%= @note["url"] || @note["id"] %>" class="status-permalink u-url">Permalink</a>
     </p>
   </div>

lib/clacks_web/views/frontend_view.ex

@@ -82,6 +82,22 @@ defmodule ClacksWeb.FrontendView do
     end
   end
 
+  @spec iso_datetime(datetime :: String.t() | DateTime.t() | NaiveDateTime.t() | Activity.t()) ::
+          String.t()
+
+  def iso_datetime(str) when is_binary(str) do
+    str
+  end
+
+  def iso_datetime(%Activity{data: data, inserted_at: inserted_at}) do
+    iso_datetime(Map.get(data, "published", inserted_at))
+  end
+
+  def iso_datetime(%{__struct__: struct} = datetime)
+      when struct == DateTime or struct == NaiveDateTime do
+    Timex.format!(datetime, "{ISO:Extended:Z}")
+  end
+
   @spec prev_page_path(conn :: Plug.Conn.t(), [
           Activity.t() | {Activity.t(), Actor.t()} | Notification.t()
         ]) ::