Story #12687: As a participant I can register myself for a conference
Implement Single Sign-On with typo3.org
We need to implement a SSO solution for the conference website that should work similarly to the login on review.typo3.org and forge.typo3.org.
The idea is, to write a new AuthenticationProvider that interacts with the SSO extension on typo3.org.
Apart from that we need to synchronize the user data (username, name, email) from typo3.org to the conference app (extracted to ticket #26634)