Summary: This makes the oauth server a bunch more useful.
Test Plan:
- used /oauth/phabricator/diagnose/ and it actually passed!
- played around with conduit via hacking URL to include access_token on a logged
out browser
- linked my account to itself by going to /settings/page/phabricator/, clicking
"link" account, then cutting and pasting the pertinent ?code=X into
/oauth/phabricator/login/.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, epriestley
Maniphest Tasks: T852
Differential Revision: https://secure.phabricator.com/D1644
be66a52050