Invoice States

In a nutshell

Invoice status tracks where an invoice is in the collection lifecycle.

Status	Meaning
`draft`	Prepared before the due date.
`open`	Due and ready for collection.
`paid`	Fully paid.
`failed`	Payment failed.
`refunded`	Reserved for refund workflows.

Status	Meaning
`PENDING_BILLING`	A payment attempt has been created.
`SUCCESS`	Payment succeeded.
`PAYMENT_FAILED`	Payment failed.
`REFUND`	Reserved for refund workflows.
`CANCELLED`	Reserved for cancelled attempts.

draft -> open -> paid
open -> failed