Support paying amountless bolt11

[thesimplekid]

cashubtc/nuts#173

[mubarak23]

@thesimplekid let me have take at this

[mubarak23]

when a mint PostMeltQuoteBolt11Response has amount set to 0, this mean the wallet is trying to get an amountless (zero-amount invoice) request invoice in the request a melt quote,

when this happen, we are going to check mint MeltMethodSetting if it's support for amountless bolt11

@thesimplekid

[thesimplekid]

No, the PostMeltQuoteBolt11Request should be extend to have an optional field as in the linked nut pr of the amount in the case of an amount less invoice. If this is supported by the mint then that amount should be paid. There should also be a check that if there is also an amount in the invoice it is the same as requested. The PostMeltQuoteBolt11Response does not need to change.

[mubarak23]

i understand, so if there is an option amount field set in PostMeltQuoteBolt11Request then mint should check if it's support amountless (zero-amount invoice), then ensure the amount field match what is in the request bolt11 Lightning invoice

[thesimplekid]

Yes.

then ensure the amount field match what is in the request bolt11 Lightning invoice

Only if there is amount included in the invoice.

[mubarak23]

Yes.

then ensure the amount field match what is in the request bolt11 Lightning invoice

Only if there is amount included in the invoice.

can an invoice comes without an amount