Authoritative flag doesn't work as expected when subnet selection fails

According to Kea ARM section 8.2.23 the Kea server should remain silent if the client is in the INIT_REBOOT state and requests an address for which the server has no lease. It should also remain silent when the client is requesting an address from a "wrong" network.

Imagine the case that the server has no configured subnets (is in migration). When the server receives a request it fails to select a subnet. It always causes the server to return a DHCPNAK. It contradicts with the authoritative specification. The server doesn't know whether or not the requested address is correct because it has no knowledge of the subnet where the client is connected.