use nostr.build api v2 with optional nip98 support (Fishcake)

add function to create nip98 http authorization header (Fishcake)

add nostr event 27235 (nip-98) (Fishcake)

pushed to damus:refs/heads/master

http://git.jb55.com/damus/commit/c464a26151046e17cd469f390a3212b8af1c9c8e.html