text: Title: I can't user user.save() to update the identifies of user
  Body: ## Description of the problem, including code/CLI snippet
  I use get user and change the identifies of it,but after use user.save(),it not changes.
  when i update user's name,it works. but if i update identifies, it not work.
  The identifies correct ,i can update it by hand.
  
  ## Expected Behavior
  after user.save() update  indetifies success
  
  ## Actual Behavior
  not work,don't get any error
  
  ## Specifications
  
    - python-gitlab version:3.14.0
    - API version you are using (v3/v4):v4
    - Gitlab server version (or gitlab.com):15.0.1
  