Only show profile status when calendar app installed

Summary:
If the calendar app is not installed we don't show the status.
Origianlly the idea was to only show the status if the viewer had access to
the app, but for display purposes this seems fine.

Fixes T5087

Test Plan: View with and without calendar installed

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T5087

Differential Revision: https://secure.phabricator.com/D9582

src/applications/people/customfield/PhabricatorUserStatusField.php

@@ -21,6 +21,11 @@ final class PhabricatorUserStatusField
     return true;
   }
 
+  public function isFieldEnabled() {
+    return PhabricatorApplication::isClassInstalled(
+      'PhabricatorApplicationCalendar');
+  }
+
   public function renderPropertyViewValue(array $handles) {
     $user = $this->getObject();
     $viewer = $this->requireViewer();