User
End customers (a user belongs to your organization)
Create a customer
Creates an end customer under your organization.
List your customers
Lists the end customers under your organization. Optionally filter by `externalId`.
Get a customer
Get a customer
Update a customer
`name` and `metadata` are updatable — `externalId` is write-once.
Delete a customer
Refused with 422 `USER_HAS_ACCOUNTS` while the customer still owns accounts.