Updates the links about license management to the help center on
the billing and upgrade pages to go to the section about the type
of license management, and to go to either the Zulip Cloud billing
article or the self-hosted billing article.
We send customer an invoice at the start of free trial, if customer
pays we upgrade them to the active plan at the end of free trial,
else we downgrade them and show a custom message on the upgrade
page regarding the current status.
Adds a link on the upgrade and billing pages that opens a stripe
billing portal for the customer to update their name and address
that will appear on invoices and receipts.
On the billing page, updating the credit card information will
no longer update the customer billing address, since they can
now do this directly through the billing portal. To be consistent
with the credit card form on the upgrade page, we still require
inputting a billing address for the card.
Note that, once an invoice is paid/complete, then changes to the
customer's name and address will not be applied to those invoices.