Don't write extra metadata for xarray in a nested dict

[jenshnielsen]

Since this prevents export to netcdf

Fixes #2922

[codecov]

Codecov Report

Merging #2934 (374a2c1) into master (d7d0c63) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2934      +/-   ##
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- Coverage   65.31%   65.31%   -0.01%     
==========================================
  Files         209      209              
  Lines       28038    28037       -1     
==========================================
- Hits        18313    18312       -1     
  Misses       9725     9725              

[guenp]

@jana-d FYI, the "extra_metadata" tag on exported xarray Datasets is going away in favor of supporting netCDF data export.

[guenp]

Thank you for fixing this bug! I have one minor suggestion to make the UT more complete but otherwise LGTM.

[jenshnielsen]

@jana-d @guenp I meant to say that this is one proposed solution. We could also merge all the data in extra_metadata (from all tags into one json string) but I think this would be cleaner? @astafan8 Any opinion

[jana-d]

I think the proposed solution is good, there is no need for the extra_metadata tag. Also agree that not merging everything into one json string might be cleaner, but happy either way.

[astafan8]

Agree with this solution as well.

the point of using the extra_metadata key to group "all aadditional metadata" was to separate it from the must-have/-be attributes, but seems to give more headache than benefit