Earlier, when adding a new user failed due to no spare licenses
available, a message was sent to the "New user announcements"
stream.
We plan to disable the stream by default as a part of improving
onboarding experience.
Now, we send a group DM to admins when adding a new user fails
due to no spare licenses available. It makes it independent of
the "New user announcements" setting. These warning messages
are important and shouldn't be missed.
Our seat count calculation is different for guest user than normal users
(a number of initial guests are free, and additional marginal guests are
worth 1/5 of a seat) - so these checks we apply when a user is being
invited or signing up need to know whether it's a guest or non-guest
being added.