Postgres has a tzrange type, which LibPQ.jl returns as an Interval[ZonedDateTime} No openness type params, so it is type unstabl
But it doesn't know if it is open or closed because LibPQ stores intervals that may be open or closed in the same postgre column type. (including mixing them).

Given we interact with intervals from prosgre databases all the time.
and we dispatch on this type param very rarely if ever,
I wonder if it wouldn;t be better stored as a field rather than a type param.

However this would be a breaking change