Revision of Cate's Data Management

[forman]

We need a slight revision of Cate's Data Management, especially a revised cate.core.ds.DataSource interface. Details are here:
https://github.com/CCI-Tools/cate-core/wiki/Revision-of-Cate's-Data-Management

• Introduce new DataSource.open_dataset API, add more constraint args, deprecate protocol arg, use new types, generalise towards any return type (forman)
• Introduce new DataSource.make_local API (forman)
• Rename LocalFilePatternDataStore and LocalFilePatternDataSource to LocalDataStore and LocalDataSource (forman)
• Reimplement all open_dataset overrides wrt deprecate protocol arg and support new constraint params (kbernat)
• Implement make_local overrides, reuse old syncmethod and Chris' new code (kbernat)
• Use new open_dataset constraint args in CLI + GUI (forman)
• Use new make_local in favor of sync where appropriate. We might keep private _sync method as an implementation detail (forman, kbernat)
• Increase cate.core.ds and cate.ds code coverage by unit-tests (kbernat)

[JanisGailis]

Looks good.

One note. When using a 'PolygonLike' from new types, one has to keep in mind that what one can get might be whatever valid polygon. Then, it depends on what OpenDAP can do, but probably a bounding box has to be extracted and used for selection.

One question though is what to do with values that are in the bounding box, but not part of the polygon. In the 'subset_spatial' operation I plan to mask these with NaN. I'm not sure what would be the best approach upon opening - mask with NaN, create a 'mask' variable, or just select the bounding box.

[forman]

..., but probably a bounding box has to be extracted and used for selection.

Yepp!

In the 'subset_spatial' operation I plan to mask these with NaN.

Please make this an optional behavior. e.g. use new kwarg mask_polygon_exterior: bool = False.

[kbernat]

Hi Norman,
in make_local method, do we need both local_name and local_id? Role of local name is obvious but how should we use second parameter, is it kind of suffix for general (ecv) name?

1. Replace sync by make_local

For this, the DataSource method sync shall be replaced by make_local and shall receive a new parameter local_id. ...

def make_local(self,
               local_name: str,
               local_id: str = None,
               time_range: TimeRangeLike.TYPE = None,
               ...