Internalize storage access for PhabricatorUserOAuthInfo

Summary:
Ref T1536. Move all access to the underlying storage to inside the class. My plan is:

  - Migrate the table to ExternalAccount.
  - Nuke the table.
  - Make this class read from and write to ExternalAccount instead.

We can't get rid of OAuthInfo completely because Facebook still depends on it for now, via registration hooks.

Test Plan: Logged in and registered with OAuth.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1536

Differential Revision: https://secure.phabricator.com/D6171

src/applications/people/controller/PhabricatorPeopleProfileController.php

@@ -64,9 +64,7 @@ final class PhabricatorPeopleProfileController
     // NOTE: applications install the various links through PhabricatorEvent
     // listeners
 
-    $oauths = id(new PhabricatorUserOAuthInfo())->loadAllWhere(
-      'userID = %d',
-      $user->getID());
+    $oauths = PhabricatorUserOAuthInfo::loadAllOAuthProvidersByUser($user);
     $oauths = mpull($oauths, null, 'getOAuthProvider');
 
     $providers = PhabricatorOAuthProvider::getAllProviders();