Parse payment vouchers embedded in requests

[NiloCK]

Checklist

• This is not a new feature or an enhancement to the Filecoin protocol. If it is, please open an FIP issue.
• This is not brainstorming ideas. If you have an idea you'd like to discuss, please open a new discussion on the Boost forum and select the category as Ideas.
• I have a specific, actionable, and well motivated feature request to propose.

Boost component

• boost daemon - storage providers
• boost client
• boost UI
• boost data-transfer
• boost index-provider
• Other

What is the motivation behind this feature request? Is your feature request related to a problem? Please describe.

Coupling individual payments with retrievals.

Describe the solution you'd like

A boost client making a retrieval request can embed a payment voucher directly into the request body - tightly coupling the individual payment with the retrieval.

MVP: Boost server should

• parse the voucher
• feed the voucher to its nitro rpc-client (api method incoming - see Small spike: Investigate sending vouchers with the boost http request go-nitro#1326)
• read the result, confirm that the voucher represents a payment, and serve the request

This improves the "accounting" for the boost server over current state (essentially: serve requests if the requester has ever paid anything).

Later:

• boost server should have a fee schedule of some sort, and be able to selective honour requests only if they cover the set fee

edit: missed the "open a blank issue" option. Haha.