Automatically create invoices

[wbobeirne]

If a webln.makeInvoice passes a fixed amount, we should just automatically generate the invoice for the website. This should be something you can configure on and off in the enable screen, if for some reason you don't want it (e.g. you need to balance liquidity.) It should also be rate limited to avoid spamming the user's node (e.g. if they request another invoice within a few seconds, either reject or prompt the user this time.)

[musdom]

If the invoice macaroon is also uploaded, users can skip the password prompt.

[fiatjaf]

Is this still being considered? Perhaps add a new flag to makeInvoice so app developers can explicitly request this -- as today they may be using makeInvoice(sat_amount) instead of the correct object as parameter the spec defines and that kinda means they don't know what they're doing and that they more-or-less expect the user to handle the invoice manually as always.

Or perhaps just require them to explicitly pass the object with the fixed amount and a description. Most apps don't pass a description, I think, and having automatic invoices created with a default description is not a good experience.