Route Blinding: allow path creator to specify incoming channel

[ellemouton]

When creating a blinded payment path for an invoice, we should allow the caller to
select the channel they want to receive on. This will allow them to force a sender to
pay over a specific channel and so gives them an extra liquidity control lever.

[alexbosworth]

Would this be incoming last hop peer or incoming channel?

[ellemouton]

Would this be incoming last hop peer or incoming channel?

good point. So on an instruction level, we tell the peer the next channel to send on. But due to non-strict forwarding, nothing stops them from choosing a diff channel that the one instructed I guess.

[MPins]

Interesting! Maybe it is a good chalange to me!

[ellemouton]

Feel free to give it a go @MPins :)

[MPins]

Thanks! Starting from the blinded paths proposal, then the code ;-)

[ellemouton]

Might make more sense to make this more general: Allow user to specify the whole path or parts of the path
(cc @alexbosworth )