Change v6 vendor-class option definition.
The idea is to change the DHCPv6 vendor-class (code 16) definition from uint32 + binary into uint32 + tuple array. This has a lot of advantages but is not backward compatible. Note if ISC DHCP allows arrays of records for Kea the array flag for a record type means the last field is an array. Currently there is only one standard option using tuples.
Quoting RFC 8415 figures 28 and 29 vendor-class option layout is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_VENDOR_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| enterprise-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. vendor-class-data .
. . . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
The vendor-class-data field is composed of a series of separate
items, each of which describes some characteristic of the client's
hardware configuration. Examples of vendor-class-data instances
might include the version of the operating system the client is
running or the amount of memory installed on the client.
Each instance of vendor-class-data is formatted as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| vendor-class-len | opaque-data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+