Today the REST API does not allow creating a user without a password.

curl \
    --header 'Content-Type: application/json' \
    --location \
    --request POST \
    --user 'admin:password' \
    'http://localhost:7990/rest/api/1.0/admin/users?name=fbar&displayName=Foo%20Bar&emailAddress=foo.bar@example.com'

This would be really useful for users that need to create various users using a script.

As it is today, a password is needed and a script to create new users would need the password configured.