Handle Stripe events not yet handled

For after #370 is implemented.

To get full coverage of relevant events, we'd want to cover these:

- [ ] `account.updated` describes an account
Occurs whenever an account status or property has changed.
- [ ] `account.application.deauthorized` describes an application
Occurs whenever a user deauthorizes an application. Sent to the related application only.
child parameters
- [ ] `account.external_account.created` describes an external account (e.g., card or bank account)
Occurs whenever an external account is created.
- [ ] `account.external_account.deleted` describes an external account (e.g., card or bank account)
Occurs whenever an external account is deleted.
- [ ] `account.external_account.updated` describes an external account (e.g., card or bank account)
Occurs whenever an external account is updated.
- [ ] `application_fee.created` describes an application fee
Occurs whenever an application fee is created on a charge.
- [ ] `application_fee.refunded` describes an application fee
Occurs whenever an application fee is refunded, whether from refunding a charge or from refunding the application fee directly, including partial refunds.
- [ ] `application_fee.refund.updated` describes a fee refund
Occurs whenever an application fee refund is updated.
- [ ] `charge.failed` describes a charge
Occurs whenever a failed charge attempt occurs.
- [ ] `charge.refunded` describes a charge
Occurs whenever a charge is refunded, including partial refunds.
- [ ] `charge.succeeded` describes a charge
Occurs whenever a new charge is created and is successful.
- [ ] `charge.updated` describes a charge
Occurs whenever a charge description or metadata is updated.
- [ ] `customer.created` describes a customer
Occurs whenever a new customer is created.
- [ ] `customer.deleted` describes a customer
Occurs whenever a customer is deleted.
- [ ] `customer.updated` describes a customer
Occurs whenever any property of a customer changes.
- [ ] `customer.source.created` describes a source (e.g., card or Bitcoin receiver)
Occurs whenever a new source is created for the customer.
- [ ] `customer.source.deleted` describes a source (e.g., card or Bitcoin receiver)
Occurs whenever a source is removed from a customer.
- [ ] `customer.source.updated` describes a source (e.g., card or Bitcoin receiver)
Occurs whenever a source's details are changed.
- [ ] `customer.subscription.created` describes a subscription
Occurs whenever a customer with no subscription is signed up for a plan.
- [ ] `customer.subscription.deleted` describes a subscription
Occurs whenever a customer ends their subscription.
- [ ] `customer.subscription.updated` describes a subscription
Occurs whenever a subscription changes. Examples would include switching from one plan to another, or switching status from trial to active.
- [ ] `invoice.created` describes an invoice
Occurs whenever a new invoice is created. If you are using webhooks, Stripe will wait one hour after they have all succeeded to attempt to pay the invoice; the only exception here is on the first invoice, which gets created and paid immediately when you subscribe a customer to a plan. If your webhooks do not all respond successfully, Stripe will continue retrying the webhooks every hour and will not attempt to pay the invoice. After 3 days, Stripe will attempt to pay the invoice regardless of whether or not your webhooks have succeeded. See how to respond to a webhook.
- [ ] `invoice.payment_failed` describes an invoice
Occurs whenever an invoice attempts to be paid, and the payment fails. This can occur either due to a declined payment, or because the customer has no active card. A particular case of note is that if a customer with no active card reaches the end of its free trial, an invoice.payment_failed notification will occur.
- [ ] `invoice.payment_succeeded` describes an invoice
Occurs whenever an invoice attempts to be paid, and the payment succeeds.
- [ ] `invoice.updated` describes an invoice
Occurs whenever an invoice changes (for example, the amount could change).
- [ ] `plan.created` describes a plan
Occurs whenever a plan is created.
- [ ] `plan.deleted` describes a plan
Occurs whenever a plan is deleted.
- [ ] `plan.updated` describes a plan
Occurs whenever a plan is updated.
- [ ] `source.canceled` describes a source (e.g., card or Bitcoin receiver)
Occurs whenever a source is canceled.
- [ ] `source.chargeable` describes a source (e.g., card or Bitcoin receiver)
Occurs whenever a source transitions to chargeable.
- [ ] `source.failed` describes a source (e.g., card or Bitcoin receiver)
Occurs whenever a source is failed.
- [ ] `transfer.created` describes a transfer
Occurs whenever a new transfer is created.
- [ ] `transfer.failed` describes a transfer
Occurs whenever Stripe attempts to send a transfer and that transfer fails.
- [ ] `transfer.paid` describes a transfer
Occurs whenever a sent transfer is expected to be available in the destination bank account. If the transfer failed, a transfer.failed webhook will additionally be sent at a later time. Note to Connect users: this event is only created for transfers from your connected Stripe accounts to their bank accounts, not for transfers to the connected accounts themselves.
- [ ] `transfer.reversed` describes a transfer
Occurs whenever a transfer is reversed, including partial reversals.
- [ ] `transfer.updated` describes a transfer
Occurs whenever the description or metadata of a transfer is updated.