Creates a new IAM user for your AWS account.
For information about limitations on the number of IAM users you can create, see Limitations on IAM Entities in the IAM User Guide.
/// The request was rejected because it attempted to create a resource that already exists.
///
/// The request was rejected because it attempted to create resources beyond the current
/// AWS account limits. The error message describes the limit exceeded.
///
/// The request was rejected because it referenced an entity that does not exist. The
/// error message describes the entity.
///
/// The request processing has failed because of an unknown error, exception or failure.
///