Review the PingOne user resource model
A user resource is a unique identity within PingOne that interacts with the applications and services in the environment to which the user is assigned.
Users are associated with an environment and a population, and the service implements directory functions to create, read, update, delete, and search for user resources. For more information, see the PingOne Platform API Reference.
The username field is required with the PingOne user resource model. This field is a string that specifies the user name, which must be unique within an environment. Limited to 128 characters in length, the username must be a well-formed email address or a string of any Unicode letter, mark (like an accent or umlaut), dot, underscore, or hyphen.