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.
Also fixes a bug in process_initial_upgrade. If you have a card on file
(e.g. from a previous subscription), and try to upgrade by billing by
invoice, neither the if nor the elif condition applies.
This will make it easier to mock the calls in our new stripe mocking
framework. I believe the two forms are equivalent, assuming the Stripe
Python bindings aren't doing anything crazy. And if not, well hopefully our
new testing framework will catch it :).
[Idea originally from Vishnu KS.]
This will improve both the maintainability and accuracy of the fixture
data. It also makes it less scary to upgrade Stripe API versions.
[With significant changes by Rishi Gupta.]
There are several situations in which we want to create a Customer and
stripe.Customer object before we really have a billing relationship with a
customer. The main one is giving non-profit or educational discounts.