Config for separate primary domain Nostr pubkey

Allow to configure a separate key for the NIP-05 address of the primary
domain vs the accounts domain.

spec/requests/well_known_spec.rb

@@ -79,10 +79,36 @@ RSpec.describe "Well-known URLs", type: :request do
     end
 
     describe "placeholder username for domain's own pubkey" do
-      it "returns the configured nostr pubkey" do
-        get "/.well-known/nostr.json?name=_"
-        res = JSON.parse(response.body)
-        expect(res["names"]["_"]).to eq(Setting.nostr_public_key)
+      describe "for primary domain" do
+        context "no different pubkey configured for primary domain" do
+          it "returns the akkounts nostr pubkey" do
+            get "/.well-known/nostr.json?name=_"
+            res = JSON.parse(response.body)
+            expect(res["names"]["_"]).to eq("bdd76ce2934b2f591f9fad2ebe9da18f20d2921de527494ba00eeaa0a0efadcf")
+          end
+        end
+
+        context "different pubkey configured for primary domain" do
+          before do
+            Setting.nostr_public_key_primary_domain = "b3e8f62fbe41217ffc0aa1e178d297339932d8ba4f46d9c7df3b61575e78fecc"
+          end
+
+          it "returns the primary domain's nostr pubkey" do
+            get "/.well-known/nostr.json?name=_"
+            res = JSON.parse(response.body)
+            expect(res["names"]["_"]).to eq("b3e8f62fbe41217ffc0aa1e178d297339932d8ba4f46d9c7df3b61575e78fecc")
+          end
+        end
+      end
+
+      describe "for akkounts domain" do
+        it "returns the configured nostr pubkey" do
+          headers = { "X-Forwarded-Host" => "accounts.kosmos.org" }
+          get "/.well-known/nostr.json?name=_"
+
+          res = JSON.parse(response.body)
+          expect(res["names"]["_"]).to eq("bdd76ce2934b2f591f9fad2ebe9da18f20d2921de527494ba00eeaa0a0efadcf")
+        end
       end
 
       context "with relay configured" do