Document the adjustment workflow and warn users about adjusting old MySQL

Summary: Ref T1191. Explain the adjustment workflow, how to resolve common errors, etc.

Test Plan: Read it, clicked doc links.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10758

src/applications/config/controller/PhabricatorConfigDatabaseController.php

@@ -62,4 +62,20 @@ abstract class PhabricatorConfigDatabaseController
     }
   }
 
+  protected function buildHeaderWithDocumentationLink($title) {
+
+    $doc_link = PhabricatorEnv::getDoclink('Managing Storage Adjustments');
+
+    return id(new PHUIHeaderView())
+      ->setHeader($title)
+      ->addActionLink(
+        id(new PHUIButtonView())
+          ->setTag('a')
+          ->setIcon(
+            id(new PHUIIconView())
+              ->setIconFont('fa-book'))
+          ->setHref($doc_link)
+          ->setText(pht('Learn More')));
+  }
+
 }