The partner the issue is attributed to. It cannot be changed after creation: an update request containing partnerId is rejected with 422.
Required for sub-operator tokens: must be one of the sub-operator's partners with access to issues; the issue is attributed to that partner. A request without partnerId, or with another partner, is rejected with 422.
Ignored for partner tokens (the issue is attributed to the token's partner).
Optional for operator and global tokens: must be a partner of the issue's operator, so a global token must also send that operator's operatorId. When omitted or null, the issue is created at operator level.