Kiosk mode [unsafe].

"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)

static/js/feature_flags.js

@@ -7,6 +7,8 @@ exports.mark_read_at_bottom = page_params.staging;
 exports.summarize_read_while_narrowed = page_params.staging;
 exports.twenty_four_hour_time = _.contains([],
                                   page_params.email);
+exports.kiosk_mode = _.contains(['role-user@customer3.invalid'],
+                                page_params.email);
 return exports;
 
 }());