Please add the description to payinvoice endpoint, if payment_request uses deschash

[rustyrussell]

Hi!

I'm trying to ensure nodes see the full invoice they're paying, but as of now that's not possible with the current LndHub protocol, since you only hand the bolt11 string which may not contain the description (LNURL particularly likes to use the h description_hash field).

This is a real problem for node validation, since they don't know what they're paying, and for users who can't query their node to see what they actually paid (especially if they use multiple front-ends).

(Note: I discovered this issue because lnbits actually has an LndHub extension which means you can actually use BlueWallet to drive CLN, which is 🔥 😮 and @callebtc reported it in ElementsProject/lightning#6092 (comment)).

[joycekerkhof]

Can you explain this for me please?