ISC DHCP per class lease limit

Quote from ISC DHCP 1dhcpd.conf.5`

PER-CLASS LIMITS ON DYNAMIC ADDRESS ALLOCATION

   You may specify a limit to the number of clients in a class that can be
   assigned leases.  The effect of this will be to make it difficult for a
   new  client  in  a  class  to get an address.  Once a class with such a
   limit has reached its limit, the only way a new client  in  that  class
   can  get  a  lease  is  for an existing client to relinquish its lease,
   either by letting it  expire,  or  by  sending  a  DHCPRELEASE  packet.
   Classes with lease limits are specified as follows:

   class "limited-1" {
     lease limit 4;
   }

   This will produce a class in which a maximum of four members may hold a
   lease at one time.

Often associated with cloned classes. Requested by a customer but a priori not easy to implement. Note that in Kea lease assignment is done before calling setReservedClientClasses.

Support tickets: support#18293, support#17523, support#19968

Being implemented in Kea.