yeah, its part of a long running PR in the blossom repo to support HTTP 402 status codes with lightning and cashu https://github.com/hzrd149/blossom/pull/29
nostr:npub138s5hey76qrnm2pmv7p8nnffhfddsm8sqzm285dyc0wy4f8a6qkqtzx624 sorry the PRs been open so long but I've wanted to thoroughly test it before its officially part of the blossom spec