Feature/oauth2

[drrr-deudeu]

MEZZO OAUTH2 LOGIN

• User login process using OAUTH2 protocol.
• In case of login success with the OAUTH2 server, the objects User, Person and SocialAccount are created or updated if needed.
• In case of login success, the user is redirected to /person and the username appears in the top bar.
• In case of logout, the user is redirected to the home page. The logout is a logout only with Mezzo, not OAUTH2 server, allowing a transparent reconnection
• The old style login stays available in case of OAUTH2_IRCAM = False

The repos touched by this enhancement are:

• mezzanine-organization
• ircam-www-theme

Operations:

• usage of django.allauth.socialaccount implies that new tables django tables are created
• https://auth.ircam.fr/ needs to be visible by the Mezzo host and the user browser
• A Social Application must be set in auth.ircam.fr/admin and mezzo/admin

[gnuletik]

• Need docs (in README.rst @yomguy ?)
• Deployment on staging planned next monday with @drrr-deudeu

[gnuletik]

• Deployment on staging done
• Logout button is not working however

[yomguy]

Huge PR @drrr-deudeu, thanks et bravo!