Include all metadata as attributes

[pont-us]

In addition to custom handling of particularly useful metadata like band centre wavelengths, we might consider automatically converting all the metadata (several MB of XML in the product archive) into attributes. Done in the simplest way, this would give all the values as strings, but we could probably apply sensible data type conversions if I can get hold of the XML schema used for EnMAP metadata (so far I couldn't track it down).

This issue was split out from this comment in the discussion of Issue #6 .

There's currently no urgent need for this feature, but it would be nice to have.

[TonioF]

Yes, I considered it, but it was not clear whether to add the metadata as dataset attributes or assign it to the various data arrays, which would make sense in some cases.