Guide users to fill Spatial information

Description of the issue

The spatial information was used quite ambiguously by users. Now the metadata spec is stricter and will not allow that level of custom metadata formats in the OEP. But as a leaning, some users wanted to force an array of locations in the oemetadata spatial element. I figured that it is useful to provide metadata that provide info on what regions the data applies. This would be in addition to the spatial extent, which should provide the scope in an aggregated fashion.

Ideas of solution

The Extent should offer a fixed selection for:

Europe
Global
Local
National
Regional

But also offer a free text option?

The location could be used to allow for an array of locations. Like States / Nuts country codes ...

Example:

if extent:National then we could add [location1:BER, location2:HAM, ....] to specify the states which the data applies to. If the Data applies to all of Germany the extent would be enough.

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md