Subscribe to a dev, musician, artist, creator in app with sats

[alltheseas]

user story

As a happy Damus Android/Notedeck user, I would like to be able to directly support a musician, an artist, or a creator by subscribing to them in app, so that I can encourage with my hard earned sats the content I want to see on nostr, and on my feed.

acceptance criteria

1. In app there is a way to "subscribe" to a particular npub (e.g. the videographer Max deMarco https://njump.me/npub1lelkh3hhxw9hdwlcpk6q9t0xt9f7yze0y0nxazvzqjmre3p98x3sthkvyz) in sats
2. Default value is $5/month displayed in sats (e.g. currently around ~~4000 sats per month)
3. User can change value to any value they see fit (1 to 1 million sats)
4. Subscription can be public, private, or anonymous
5. User can see their subscription status (i.e. "subscribed")
6. User can unsubscribe

context & discussion

-this is practically prohibited by Tim Apple/iOS.
-is there a subscription NIP?
-see highlighter.com implementation by Pablo

pre-requisites

#237
damus-io/notedeck#175
#228

[alltheseas]

NIP-88

nostr-protocol/nips#866