Transaction API-first lifecycle

Transaction statuses can be updated at various points in the Transactions lifecycle to track user progression through API-first flow.

To start we suggest the following statuses but as we build out the integration we can add/remove them as necessary. These can be used for tracking/reporting:

Status	Event Name	Description	Metrics
`created`	`created-at`	Initial status. Transaction has been created with information collected and passed to Persona. The `created-at` attribute on the Transactions notes when this happens.
`completed`	`transaction.status-updated` with status `completed`	The verifications have been run and the outcome is `passed`.	Completed Rate = Completed / Created
`approved`	`transaction.status-updated` with status `approved`	The Transaction has been approved. Will be using `transaction.status-updated` with status `approved`.	Approved Rate = Approved / Created
`declined`	`transaction.status-updated` with status `declined`	The Transaction has been declined. Will be using `transaction.status-updated` with status `declined`	Decline Rate = Declined / Created