Fixes incorrect auth proxy link.
Update index page to link to v6.4 (currently latest).
Adds What's new in v6.5 draft article.
(cherry picked from commit 073e9ef9e7)
* AuthProxy: Can now login with auth proxy and get a login token
* added unit tests
* renamed setting and updated docs
* AuthProxy: minor tweak
* Fixed tests and namings
* spellfix
* fix
* remove unused setting, probably from merge conflict
* fix
* OAuth: github team sync POC
* OAuth: minor refactor of github module
* OAuth: able to use team shorthands for github team sync
* support passing a list of groups via auth-proxy header