metadata is None after aggregate_spatial

[VincentVerelst]

After applying aggregate_spatial to a Rastercube, the resulting Vectorcube does not contain any metadata anymore.

[soxofaan]

This is not as straightforward as hoped, as some vector cubes details are not settled yet. But maybe there are some quick wins already possible without having to over-engineer a general solution, so:

what do you want to use the metadata for? Any particular fields, e.g. you just want the band names?

[VincentVerelst]

Yes, having the band names would be the most important.

[soxofaan]

related to #464 #425 #527

[jdries]

I would say aggregate_spatial preserves band names when going from raster to vector, so can we just copy that part of the metadata? Maybe @VincentVerelst can prepare a PR for that?