Bill Users for Paid Accounts

[stephenprater]

What changes does this PR introduce?

This enables us to bill users through Stripe for Paid Accounts

Any background context you want to provide?

There are a few major parts to this PR:

1. Upload Plan data to stripe consistently
2. Add "foreign keys" to models to maintain their connection to stripe.
3. Allow users to update their records via the API
4. Keep those changes in sync with Stripe
5. Respond to Stripe initiated changes via webhook and keep those changes in sync with our tables.

As an outgrowth of 3/4/5 I discovered that our use of SQLAlchemy made the models both hard to test in isolation and likely to result in a lot of specious calls to stripe. We needed better controls of the change management than SQLAlchemy's (coarse) callbacks offered, so we need to track changes ourselves. About half of our interaction methods need to either flush or commit to the DB, but it's it's confusing to have a lot of database state management mixed in with business logic.

To avoid that, I created an Interactor mixin that let's us manage that kind of housekeeping a little more decoratively.

Where should the reviewer start?

I tried to order these commits in a logical order so it made sense when you read them instead of a single 5,000 line diff - so you should be able to start at the top.

Has this been manually tested? How?

Tests pass! This one is definitely going to need pushbutton.

What value does this provide to our end users?

Let's them pay us for our awesome service, keeping us all employed and our service running!

What GIF best describes this PR or how it makes you feel?

[stephenprater]

Allow Users to Change their Plans

[AndrewScibek]

I started to review it and then started to think that it seems weird to include all our billing logic in this repo. There is nothing to hide and idk where else you would put it but seems like something that isnt needed in the repo. Thoughts?

Edit:
After discussion today it seems we will indeed split this work away from holepunch at a later date. It is not needed immediately but could make our life easier down the road

[stephenprater]

Allow Users to Change their Plans

change made