For large instance, the size of a cluster infos event is quiet large
(1MB) and is sent every second. If these events are queued, it can takes
a lot of RAM. The time limit ensure that such events don't stay in queue
if they are not processed quickly, as they are all the same, one in the
queue is enough.

Adapt calendar web service to not use the identity name, add a new user
authentications web service based on identity key, remove the advanced
properties controller

Login happens only with authentication informations, identity name is
now only used for legacy directory name. User name of authentication can
be changed. LDAP users can be imported with LDAP::ldapUid. Users can be
imported in courses, groups... with First name last name.

Implement a CSRF token to protect a little more against CSRF attack.
Enhance the UI framework to allow opening a link in a new browser
window.

Use an opt-out flow for comments in video, springify notifications and
notifications handlers