Fix bugs in datacube extension.

[huard]

• Add test.
• Add schema for local validation.

[huard]

So the tests run fine locally, and I don't quite understand why the datacube one fails on the CI.

[huard]

I traced the problem to pystac. Works with 1.8.3, fails with 1.9.0.

[dchandan]

Oh I see, this is from Pathlib

[huard]

I don't have permission to merge, let me know if there's anything else to modify.

[dchandan]

I also can't seem to merge anymore. @fmigneault did you make any aches changes after taking over from Mathieu? Please give David and I elevated permissions.

[fmigneault]

You should both be able to merge as long as there was 1 review approval from someone else.