Saving sparse (or duck) arrays in datasets to file

[renecotyfanboy]

Is your feature request related to a problem?

As the sparse package seems to grow in the ecosystem, I have integrated the combination of xarray and sparse in the package I am currently developing. I have experienced the power of duck-array features in xarray, since it took less than 10 minutes to convert the matrix involved to a sparse matrix and get all the tests to green. However, datasets involving sparse arrays can't be exported to netcdf files at this time.

Describe the solution you'd like

It would be great to think about some sort of interface so that the sparse (and maybe more generally duck) arrays could be serialized using declared methods.

Describe alternatives you've considered

At this time, I am converting the sparse entry to dense before saving them, which is fine but kinda loses the point of using it. I think I will write a custom loader/unloader using the coords/data interface of the sparse package at some point.

Additional context

No response

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[dcherian]

Closing as duplicate of #4156.

Can you reply there with answers to these questions please:

1. Which sparse format are you using?
2. Do any of the CF-compliant representations work better for your use case?