Creates an association between a Tag (entity) and a PeopleAsset.
If the assignment already exists, it returns the existing record (idempotent).
Provide either employee_id or people_asset_id to identify the person.
If both are provided, people_asset_id takes precedence.
Device-specific API token generated from the Tester device's edit page. Each token is unique to a Tester device and scopes all operations to that device's brand.