"Kiosk mode" is a "read-only" Zulip suitable for embedding into
an iframe on another site. I say "read-only" in quotation marks,
because the account is still a fully-fledged active account on
the server, and we just tear out a bunch of stuff in Javascript
(that a malicious user could easily re-enable).
So in that sense, it's not actually safe in security-sensitive
environments -- malicious users logged in via kiosk mode
can do anything the kiosk-mode user can do.
(We need this functionality for the customer3 realm specifically;
we'll possibly just tear this code back out once that experiment
has run its course.)
(imported from commit deb035b4c702fcdb0e660ed549fe74c682abb6d9)
When you read messages in a narrow and then un-narrow, collapse
adjacent messages read in the narrow into a summary row that can
be clicked to expand those messages.
Scoped to staging with feature flags.
The implementation of this within our current MessageList is rather ugly.
(imported from commit bcb3a39d8c0c334136fe86318f18ead03f0f50bf)