Reference
USER_ALREADY_EXISTS
User already exists
User already exists
HTTP status 409 Conflict, code USER_ALREADY_EXISTS.
What it means#
A user with that email already exists in the organisation.
What to do#
Assign roles to the existing user instead of creating another.
On the wire#
Every error response carrying this code names this page in error.moreInfo,
with the request id in the query string. See Error codes for
the response shape and the list of every code.