UUID version 6 is a field-compatible version of UUIDv1, reordered for
improved DB locality. It is expected that UUIDv6 will primarily be
used in contexts where there are existing v1 UUIDs. Systems that do
not involve legacy UUIDv1 SHOULD consider using UUIDv7 instead.
If 'node' is not given, a random 48-bit number is chosen.
If 'clock_seq' is given, it is used as the sequence number;
otherwise a random 14-bit sequence number is chosen.
