cb-cmds: empty value for next-server parameter is accepted which causes misconfiguration
It cases a failure during lease assignment:
2019-04-17 07:52:58.700 DEBUG [kea-dhcp4.bad-packets/6301] DHCP4_PACKET_DROP_0007 [hwtype=1 08:00:27:f9:dd:64], cid=[no info], tid=0xf52d94: failed to process packet: Failed to convert string to address '': Invalid argument
If value and its format can be validated upfront during accepting configuration in cb-cmds it should be done to avoid extra effort of debugging misbehaviour of Kea.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information