unique check for url name

app/models/domain/user/fa_user.rb

@@ -12,7 +12,8 @@ class Domain::User::FaUser < Domain::User
   has_many :user_post_favs,
            class_name: "Domain::UserPostFav",
            foreign_key: :user_id,
-           inverse_of: :user
+           inverse_of: :user,
+           dependent: :destroy
 
   belongs_to :last_user_page_log_entry,
              foreign_key: :last_user_page_id,
@@ -34,7 +35,7 @@ class Domain::User::FaUser < Domain::User
        prefix: :state
 
   validates :name, presence: true
-  validates :url_name, presence: true
+  validates :url_name, presence: true, uniqueness: true
   validates :state, presence: true
 
   # validates :account_status,