WIP: Improve Nostr user metadata fetching

Use a multi-step process, caching results in between, while informing
the user about the current steps/progress

app/services/nostr_manager/discover_user_relays.rb

@@ -1,8 +1,8 @@
 module NostrManager
   class DiscoverUserRelays < NostrManagerService
-    def initialize(pubkey:)
+    def initialize(pubkey:, relays: nil)
       @pubkey = pubkey
-      @relays = Setting.nostr_discovery_relays
+      @relays = relays.present? ? relays : Setting.nostr_discovery_relays
     end
 
     def call