feat: prevent join requests with equal mail

test/membership/join_request_approval_domain_test.exs

@@ -67,6 +67,18 @@ defmodule Mv.Membership.JoinRequestApprovalDomainTest do
     end
   end
 
+  describe "reviewed_by_display" do
+    test "get_join_request returns reviewed_by_display so UI can show reviewer without loading User" do
+      request = Fixtures.submitted_join_request_fixture()
+      reviewer = Fixtures.user_with_role_fixture("normal_user")
+
+      assert {:ok, _} = Membership.approve_join_request(request.id, actor: reviewer)
+
+      assert {:ok, loaded} = Membership.get_join_request(request.id, actor: reviewer)
+      assert loaded.reviewed_by_display == to_string(reviewer.email)
+    end
+  end
+
   describe "reject_join_request/2" do
     test "reject does not create a member" do
       request = Fixtures.submitted_join_request_fixture()