This is a major rewrite of the billing system. It moves subscription
information off of stripe Subscriptions and into a local CustomerPlan
table.
To keep this manageable, it leaves several things unimplemented
(downgrading, etc), and a variety of other TODOs in the code. There are also
some known regressions, e.g. error-handling on /upgrade is broken.
A lot of the seemingly unrelated test fixture changes are because we're
removing a query to stripe in the upgrade path, in cases when the user's
realm has an existing Customer object.
Rishi Gupta
Vishnu Ks