The field proj:epsg has been deprecated in v1.2.0 in favor of proj:code and has been removed in v2.0.0. For example, the former field "proj:epsg": 32659 must be migrated to "proj:code": "EPSG:32659".
We seem to use "proj:epsg" in various places in openeo-python-driver and openeo-geopyspark-driver
found this out from working on https://github.com/ESA-APEx/apex_algorithms/issues/38:
from https://github.com/stac-extensions/projection:
We seem to use "proj:epsg" in various places in openeo-python-driver and openeo-geopyspark-driver