Use the new preview_text method of jmap_email to generate
clean snippet for thread (denormalized at update_stats)
and message (at serialization). Now when a mesage is folded, we
display this snippet. In the thread list we also display this snippet above
the subject.
When a user tries to access to a message route when it is not
authenticated, it is redirect on the homepage and have to authenticate.
Now in this case, we redirect on homepage and persist the previous route
within a next query param, in this way, we are able to automatically
redirect the user on the right view once it is authenticated.
Notably, we try to reduce disk usage by standardizind on common
base Docker images. We also improve node_modules by reducing
duplicate dependencies and install speed.