Now that we split between Signer (Amber) and Nostr App (Amethyst), who wants to develop the local Relay App?

It's basically the same structure: Use Android's Content Resolvers to communicate between apps in the background. Nostr filters are translated to queries. The goal is to save all posts from the author or to the author on the phone and have some db management actions in place to clean things up here and there.

In that way, we won't have duplicated databases for each Nostr app.