cln-bip353: add plugin that fetches payment instructions from human readable addresses

[daywalker90]

Changelog-Add: new plugin cln-bip353 that can fetch payment instructions from human readable addresses

Important

25.09 FREEZE July 28TH: Non-bugfix PRs not ready by this date will wait for 25.12.

RC1 is scheduled on August 11th

The final release is scheduled for September 1st.

Adds a new rpc command fetchbip353 [address] that fetches payment instructions from a bip-353 address and returns an object containing:

• proof: lowercase hex encoded proof
• instructions: An array of bip353 payment instruction objects

These objects either contain an onchain instruction:

• onchain: a bitcoin address
• onchain_amount_sat: an optional amount for fixed amount payments
• description: an optional description provided by the recipient

or an offchain instruction:

• offer: a bolt12 offer string
• offchain_amount_msat: an optional amount for fixed amount payments
• description: an optional description provided by the recipient

Fixes: #8361

Checklist

Before submitting the PR, ensure the following tasks are completed. If an item is not applicable to your PR, please mark it as checked:

• The changelog has been updated in the relevant commit(s) according to the guidelines.
• Tests have been added or modified to reflect the changes.
• Documentation has been reviewed and updated as needed.
• Related issues have been listed and linked, including any that this PR closes.

[daywalker90]

Added a basic test with the same address the library uses in it's tests. Let me know if you have more addresses you'd like to see tested.

Also updated the bitcoin_payment_instructions library to an unreleased version that supports proxying and implemented proxying incase always_use_proxy is set.

For documentation i've added a json schema file.

I have reworked the reponse structure a bit to also support onchain instructions.

[rustyrussell]

Great! The always-use-proxy was my only question on this PR.

Ack d669e6f

[daywalker90]

rebased after merge of wss-proxy which created some conflicts.