Want to display filter user list in taxonomy term


I make a taxonomy and want to add a user list field which display a specific roles user. While adding the term it shows the dropdown of specific role.

For this I have made a field of type enitiy reference And also it is showing the users list in this dropdown. But I have something a different requirment like If a user is assciated with any term, and while adding another term this user should not display in this user dropdown.

For exp: there is taxonomy of type workspace and while adding the term Suppose ‘A’ user assciate with this term so this user ‘A’ would not be display when we add next term. In short we can say that one user is only associate with only one term. So

Anyone could help in this it will be helpful for me.

Thanks in advance 🙂

Drupal version: 

Source: https://www.drupal.org/taxonomy/term/4/feed