Refactor Nostr settings/connect

* Use NIP-42 auth event instead of short text note
* Verify event ID and signature using the nostr gem instead of custom code

app/services/nostr_manager/validate_id.rb

@@ -1,11 +0,0 @@
-module NostrManager
-  class ValidateId < NostrManagerService
-    def initialize(event:)
-      @event = Nostr::Event.new(**event)
-    end
-
-    def call
-      @event.id == Digest::SHA256.hexdigest(JSON.generate(@event.serialize))
-    end
-  end
-end

app/services/nostr_manager/verify_auth.rb

@@ -0,0 +1,17 @@
+module NostrManager
+  class VerifyAuth < NostrManagerService
+    def initialize(event:, challenge:)
+      @event = event
+      @challenge_expected = challenge
+      @site_expected = Setting.accounts_domain
+    end
+
+    def call
+      site_given      = @event.tags.find{|t| t[0] == "site"}[1]
+      challenge_given = @event.tags.find{|t| t[0] == "challenge"}[1]
+
+      site_given == @site_expected &&
+      challenge_given == @challenge_expected
+    end
+  end
+end

app/services/nostr_manager/verify_signature.rb

@@ -1,17 +0,0 @@
-module NostrManager
-  class VerifySignature < NostrManagerService
-    def initialize(event:)
-      @event = Nostr::Event.new(**event)
-    end
-
-    def call
-      Schnorr.check_sig!(
-        [@event.id].pack('H*'),
-        [@event.pubkey].pack('H*'),
-        [@event.sig].pack('H*')
-      )
-    rescue Schnorr::InvalidSignatureError
-      false
-    end
-  end
-end