Fix notification message when Aphlict is not configured

Summary:
Before this change the footer in the notification bar was a bit
weird on the message "Notification server not enabled":

| Before | After |
|-----------|-----------|
| {F315024} | {F315001} |

Also a bit wrong on the "Connecting..." message:

| Before | After |
|-----------|-----------|
| {F315061} | {F315072} |

The fix involves a refactor in the HTML structure in order to
match the graphic rendered when Aphlict is configured and running.

In short, we pass from this:

COUNTEREXAMPLE
<span class="connection-status-text aphlict-connection-status-notenabled">
<span class="visual-only phui-icon-view phui-font-fa fa-circle-o grey"></span>
Notification server not enabled
</span>

To this:

<span class="visual-only phui-icon-view phui-font-fa fa-circle-o grey"></span>
<span class="connection-status-text aphlict-connection-status-notenabled">Notification server not enabled</span>

See the Task for additional details.

Closes T15415

Test Plan:
Follow the official Notification documentation about the config `notification.servers`,
open the Notification top-bar, and check the message in these conditions:

- without the config
- with the config
- with/without Aphlict running

https://we.phorge.it/book/phorge/article/notifications/

Reviewers: O1 Blessed Committers, avivey

Reviewed By: O1 Blessed Committers, avivey

Subscribers: avivey, speck, tobiaswiese, Matthew, Cigaryno

Maniphest Tasks: T15415

Differential Revision: https://we.phorge.it/D25312

src/applications/notification/view/PhabricatorNotificationStatusView.php

···
   protected function getTagContent() {
     $have = PhabricatorEnv::getEnvConfig('notification.servers');
     if ($have) {
-      $icon = id(new PHUIIconView())
-        ->setIcon('fa-circle-o yellow');
-      $text = pht('Connecting...');
-      return phutil_tag(
-        'span',
-        array(
-          'class' => 'connection-status-text '.
-            'aphlict-connection-status-connecting',
-        ),
-        array(
-          $icon,
-          $text,
-        ));
+      return $this->buildMessageView(
+        'aphlict-connection-status-connecting',
+        'fa-circle-o yellow',
+        pht('Connecting...'));
     } else {
-      $text = pht('Notification server not enabled');
-      $icon = id(new PHUIIconView())
-        ->setIcon('fa-circle-o grey');
-      return phutil_tag(
-        'span',
-        array(
-          'class' => 'connection-status-text '.
-            'aphlict-connection-status-notenabled',
-        ),
-        array(
-          $icon,
-          $text,
-        ));
+      return $this->buildMessageView(
+        'aphlict-connection-status-notenabled',
+        'fa-circle-o grey',
+        pht('Notification server not enabled'));
     }
+  }
+
+  /**
+   * Create an icon and a message.
+   *
+   * @param  string $class_name Raw CSS class name(s) space separated
+   * @param  string $icon_name  Icon name
+   * @param  string $text       Text to be shown
+   * @return array
+   */
+  private function buildMessageView($class_name, $icon_name, $text) {
+    $icon = id(new PHUIIconView())
+      ->setIcon($icon_name);
+
+    $message = phutil_tag(
+      'span',
+      array(
+        'class' => 'connection-status-text '.$class_name,
+      ),
+      $text);
+
+    return array(
+      $icon,
+      $message,
+    );
   }
 
 }