This will edit the "Define a list of custom ICE servers" section in the
"Configure ICE servers with Twilio" v15.0 user doc. I added a line to
mention that defining a list of custom ICE servers is an optional step,
as Odoo only uses this list as a fallback if Twilio is not configured or
is not working at any given moment.
Fixes PR #1994
Closes Odoo Task 2882679
closesodoo/documentation#2240
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>
