Not able to understand how user_entitlement is being used in azure_devops

Hello Team,
i have been trying to automate and manage complete azure devops via terraform.I have following issue.

  1. i could not understand why we have to use user_entitlement.Did not understand it.Doc just say it used to managed users in azure devops and there permission
  2. My doubt is suppose i already have set of users added in azure devops organisation along with proper lic(basic).
  3. Now i want to fetch user’s id so i can use them in the auto-reviewer-add option.
  4. But when i use Data Source: azuredevops_users.It does not output the correct the user-id.
  5. My point is if i already have user present.How can i fetch there correct user id rather again going and running azuredevops_user_entitlement
  6. As per my understand i see azuredevops_user_entitlement is technically adding/creating the user in organisation. Correct me if i am wrong?
    Requesting for please help on this.As its blocking me out.