Include CBERS-4 MUX example about stac-spec

[cholmes]

That'd be awesome @fredliporace! Though hold off for a bit, as we're in the midst of shifting some core fields. The dev branch should have an almost up to date json schema (except time stamp needs to be udpated), but it doesn't have the updated samples yet. I'm hoping to do that this week. Also cc @matthewhanson who is working on an Earth Observation profile, which will be relevant to share more fields past just the core.

[cholmes]

See https://github.com/radiantearth/stac-spec/milestone/3 for the issues that are settling in soon.

[matthewhanson]

@fredliporace I'm working on the EO profile/extension now, I'll have a PR up by tomorrow, then I think it's a good time to have examples of actual data (as @cholmes said, the EO profile will make the examples more relevant). I'll be able to provide some for landsat-8 and sentinel-2.

[fredliporace]

@matthewhanson @cholmes OK, I'm already working on an exercise to generate a CBERS-4 MUX Item using the current spec, it seems to me that an adaptation to the new spec will be then easier.

The mapping between CBERS-4 MUX metadata and STAC seems to be straightforward. The only question that occurs to me at this point is how to deal with the multiple CBERS-4 payloads, 4 cameras with distinct features. In that particular sense CBERS is different from LS8(*)/S2.

Anyway, I'll review that considering the new spec/profiles as soon as they are available.

(*) LS8 OLI/TIRS are distinct cameras but generate data 'in tandem' and with similar geometric characteristics/coverage, which is not the case for CBERS-4.

[matthewhanson]

@fredliporace That sounds like the right approach to me. The different CBERS-4 instruments would be different collections, or products, see #63

[fredliporace]

Implementation in #77

[cholmes]

I think we didn't quite get this finished for 0.4.0. I'm happy to merge in before a 0.5.0 'release' since it's just an example in the core stac repo.

[fredliporace]

Changing issue scope, see #98

[fredliporace]

Duplicate of #98