Maintenance: Small update of

Message-Id: 202012181800
Time: beginning 21st Dec 9am
Affected: Users of Jupyter
Impact: Short loss of connectivity

The service receives a small update Monday 21th, around 09am. The
update adds a welcome page to the service with a few helpful information about the service
and prevents the immediate request to sign in without providing context as to why.
During the update the webserver will be restarted briefly and access to running notebooks
will be interrupted for < 5min. The running notebooks themselves will not be interrupted.