Instead of requiring an update to a host's facet attributes to include the ID of the facet, look up the needed ID in the API controller and add to params. Facet IDs are not, imho, a user-facing aspect that needs to be exposed.

{
    host_id: 123,
    host: {
        name: "abc.example.com",
        content_facet_attributes: {
            id: 1234,    <---- REMOVE
            lifecycle_environment_id: 12,
            content_view_id: 12
        },
        subscription_facet_attributes: {
            id: 1234,    <---- REMOVE
            service_level: "Premium" 
         }
    }
}