special notation which shrinks excluded prefix is wrong
the address "excluded-prefix": "3001:db8:9:0:0:cafe::" is properly returned back by kea as 3001:db8:9:0:0:ca00::/88
but the truncation is wrong (double set of "::" which is invalid, and also "::0" which is invalid):
the expansion is bitwise correct: 3001:db8:9::ca00:0:0 but the expanded version is 3001:0db8:0009:0000:0000:ca00:0000:0000 so the prefered version is 3001:db8:9:0:0:ca00::
the last part might be a Kea issue:
Kea returns it as: