This uses an actual query to the backend to check if the subdomain is
available, using the same logic we would use to check when the
subdomain is in fact created.
The issue is that the server wants to display an error when you make a
request and fail, but the jQuery form validator also wants to display
errors at the same time. This removes the server errors to display the
jQuery.
Fixes: #8239.
This presents multiple states for the subdomain input option
depending on the existence of a root domain.
Commit modified heavily by Brock Whittaker <brock@zulipchat.com>.
Fixes#6863.
This adds some configuration options to settings.py, namely
PASSWORD_MIN_LENGTH and PASSWORD_MIN_QUALITY, which control
when the frontend validator invalidates the password.
Closes#2628
