WORKSPACES-1965 forced us to remove ICS links on emails as we needed to protect those links, however such feature may still be usefull.

We should have a better handling of ICS for calendar and tasks that still take into account the fact that we do not want to share a public link.
A good way to do it would be to add a static ICS corresponding to the event/task the moment it has been created/updated. This may also be usefull for some email software that handle directly ICS on mail attachment, to link it directly to their calendar for example