does atMost(1) matcher rule break postel's law? Because let's say atMost(0) that's probably not allowed, because you're basically saying "return empty list", which is akin to say "return no list" which breaks this https://docs.pact.io/getting_started/matching/gotchas#you-cannot-expect-a-field-to-not-be-present-in-a-response but does saying atMost(1) also break the clause "you cannot test for absence of something", cause you're testing for absence of elements beyond 1?

I think that should be a guiding principle and not an absolute law. If using

atMost(1)

makes sense to use, then people are stating they never expect more than one value.