Previously, sending a gift badge was not a durable operation, which
meant that crashes/failures could cause users to have their payment
methods charged without actually sending the badge.
Now, the flow is split up into two steps: non-durable parts before the
charge is attempted, and durable parts afterward.
The high-level flow is:
1. Prepare the payment, which involves a couple of repeatable network
requests.
2. Enqueue a job with the prepared payment, that:
1. Charges the payment method (idempotently)
2. Requests a receipt credential (idempotently)
3. Enqueues a gift message, and optionally a text message
3. When the job completes, open the conversation in the UI.
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