The X-Scope-Identifier header plays a crucial role when creating a Subject for the Organization UNIT (formerly, Asset UNIT).
It defines the scope in which the Subject is created, ensuring that the generated API_KEY is tied to a specific Organization UNIT.
Note: If this header is omitted, the following error message will be displayed:
"message": "The request functionality is not implemented yet. ['Subject::API_KEY' creation not supported for none 'Organization::UNIT' scopes]"
Other use case
See article: How to add an additional level to your structure