I think to implement this in a client, you need to look at both of these pages...

https://github.com/nostr-protocol/nips/issues/1843

https://github.com/nostr-protocol/nips/pull/2063

And then look again right here: https://github.com/nostr-protocol/nips/blob/master/47.md#pay_invoice

... look at that `metadata` field

.... and then look here :

https://github.com/nostr-protocol/nips/blob/master/47.md#metadata

.. specifically at this part:

```

"nostr": {

"pubkey": "string",

"tags": [],

// ...

}, // NIP-57 (Nostr Zaps)

```