[suggestion] - implement invoices

[katmai]

keepers need to have an easy way to have invoices available to them for their work. https://request.network protocol can be leveraged to solve this in an elegant way.

[RequestRobbin]

@andrecronje happy to assist you there if this is of even the slightest of interest. We've built a protocol for the last years (and a product on top of that protocol recently called Request Invoicing) that utilizes IPFS + Ethereum for invoice issuance, payments & payment detection (which together create triple-entry bookkeeping possibilities).

If this can be of use for either keepers or job posters, do let me know. I'm @RobbinRequest on Telegram if that's easier.