Include expiry in invoices

[jkczyz]

When creating an Invoice using functions in the lightning-invoice crate's utils module, the invoice expiration is not set. It should be set with the value encoded in the provided payment secret. Otherwise, BOLT 11 defines the default expiry to be 1 hour whereas ChannelManager will use whatever value is encoded in the payment secret.

This may be tricky because either the methods will need to take in a ChannelManager to verify the payment secret and extract the expiry or the expiry needs to be passed in but could potentially not match what's encoded in the payment secret.

[dunxen]

I can try pick this up. Would be some alright exposure to lightning-invoice crate :)

[jkczyz]

Great! Also, note that his only is a problem for create_phantom_invoice and create_phantom_invoice_with_description_hash. The other utility functions take a ChannelManager and use DEFAULT_EXPIRY_TIME.

[dunxen]

Seems only the second option would make sense in this case as requiring a ChannelManager would defeat the purpose of #1384 😅. However, then we are stuck with the possibility of the expiry not matching what's encoded as you mentioned.

[TheBlueMatt]

I don't think at need to worry about the expiry not being encoded properly - you can't use phantom nodes without it so if the expiry isn't encoded correctly we should be erroring anyway. Does seem like this needs to be based on #1384.

[jkczyz]

We may want to consider having the phantom invoice utility functions directly call the exposed creation functions from #1384 instead of exposing functions for decoding. Then the interface would more closely match the non-phantom invoice utility functions.

[TheBlueMatt]

Adding to 107 cause it's an oversight we should fix, but if it slips no big deal.

[dunxen]

I see #1384 is merged so will get back to work on this. Spread myself a bit thin with the Qala.dev stuff 🥲

Edit: Should have a PR out on Friday. Have been working on it today.

[jkczyz]

Re-opening since while #1422 added an invoice_expiry_delta_secs to the utility functions, it didn't set expiry on the Invoice itself. Also, we should allow passing invoice_expiry_delta_secs to the non-phantom utilities for those not wanting the implicit default expiry.

[dunxen]

Will fix today.