Server side web monetization validation

[wilsonianb]

c8s currently uses react-web-monetization to restrict functionality to users paying via web-monetization.

However, users can spoof web monetization events without actually paying, so the c8s server needs to verify payments before handling requests

Possible solutions:

• web-monetization-access (requires btp uplink/moneyd)
• spsp server functionality is extended to allow users to query ILP wallet providers to verify received web monetization payments

[wilsonianb]

Replaced by https://github.com/wilsonianb/c8s/issues/47