Allow Mastodon address domain to be different from primary domain

spec/models/user_spec.rb

@@ -12,6 +12,38 @@ RSpec.describe User, type: :model do
     end
   end
 
+  describe "#mastodon_address" do
+    let(:user) { build :user, cn: "jimmy", ou: "kosmos.org" }
+
+    context "Mastodon service not configured" do
+      it "returns nil" do
+        expect(user.mastodon_address).to be_nil
+      end
+    end
+
+    context "Mastodon service configured" do
+      before do
+        Setting.mastodon_enabled = true
+      end
+
+      describe "domain is the same as primary domain" do
+        it "returns the user address" do
+          expect(user.mastodon_address).to eq("jimmy@kosmos.org")
+        end
+      end
+
+      describe "domain is different from primary domain" do
+        before do
+          Setting.mastodon_address_domain = "kosmos.social"
+        end
+
+        it "returns the user address" do
+          expect(user.mastodon_address).to eq("jimmy@kosmos.social")
+        end
+      end
+    end
+  end
+
   describe "#is_admin?" do
     it "returns true when admin flag is set in LDAP" do
       expect(Devise::LDAP::Adapter).to receive(:get_ldap_param)