Track current requirements for Stripe Connect

[excid3]

1. When a account.updated event comes through, request the Account through the API.
2. Look at requirements.currently_due to see if there are any
3. Change onboarding_complete to a state [pending, needs_attention,complete] so that we can show the middle state when a user needs to give Stripe more information.

[excid3]

Possibly need to listen to a deauthorized webhook when a Standard account gets disconnected.

[mrjonesbot]

When creating payment_processors (customers), allow an option to pass merchant_id to set_payment_processor such that when payment_processor.customer is called for the first time, it creates a customer for the merchant account.

e.g.

@user.set_payment_processor :stripe, merchant_id: acct_123456789
@user.payment_processor.customer #=> Customer for merchant account #acct_123456789

[excid3]

@mrjonesbot you can already do that.

@user.set_payment_processor :stripe, stripe_account: "acct_1234"

[mrjonesbot]

@mrjonesbot you can already do that.

@user.set_payment_processor :stripe, stripe_account: "acct_1234"

Whoops, I guess I didn't read the definition well enough 😓

Maybe I'll open a PR to update the README