AIXE endpoint: /aixe/management/assign-service-provider-to-cleaning-items
Discovery request: GET /aixe/management/assign-service-provider-to-cleaning-items/?
Action request: POST /aixe/management/assign-service-provider-to-cleaning-items

Purpose:
Assigns one service provider to one or more cleaning invoice items.

Required fields:
BusinessKey, InvoiceKey, ServiceProviderKey, InvoiceItemKeys.

Optional fields:
ScheduledStartDate.

Rules:
Any active assignment to another provider for the same item is deactivated.

Response convention:
SuccessCode is SUCCESS when the operation completes. Success is true on success. Errors return SuccessCode ERROR, Success false, and a Message. Numeric database IDs are never returned.