Attach an existing project to the tenancy unit as a new tenant resource. The project could either be the tenant project reserved by calling AddTenantProject under a tenancy unit of a service producer's project of a managed service, or from a separate project. The caller is checked against a set of permissions as if calling AddTenantProject on the same service consumer. To trigger the attachment, the targeted tenant project must be in a folder. Make sure the ServiceConsumerManagement service account is the owner of that project. These two requirements are already met if the project is reserved by calling AddTenantProject. Operation.