Search by datetime in CQL Text

[m-mohr]

Describe the bug
As datetime is not supported directly, as seen in #100, I'm now trying to use CQL which was mentioned as alternative.

I want to filter by timestamp on the datetime field, e.g.
https://planetarycomputer.microsoft.com/api/stac/v1/collections/chloris-biomass/items?limit=12&filter-lang=cql2-text&filter=datetime < TIMESTAMP('2010-01-01T01%3A00%3A00.000Z') (also tried the URL encoded variant)

Instead of results that are older than 2010, I also get results that are newer than 2010. It looks like the filter is not taken into account at all.

Is CQL not supported on the items endpoint? Some of the conformance classes around filtering are a bit of a mess in stac-fastapi and stac-api-spec currently, so I'm just guessing...

To reproduce
See above.

Expected behavior
See above.