Enable object_codec in zarr backend

[vrishk]

What is your issue?

The issue is that I am not able to define a custom object codec and use it for encoding particular variables in an xarray Dataset. I found a workaround that requires small changes to two files as follows.

Currently in the zarr backend of xarray, the allowed keys in the encoding dictionary are

{
        "chunks",
        "compressor",
        "filters",
        "cache_metadata",
        "write_empty_chunks",
}

Would it be possible to add object_codec to enable the use of custom codecs on object datatypes (change in xarray/backends/zarr.py)? Also would require ensure_dtype_not_object to be removed from conventions.py and placed in the backends as the TODO there suggests.

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[kmuehlbauer]

@vrishk Sorry for the delay here and thanks for bringing this to attention. We now have at least two requests which might move this forward (moving ensure_dtype_not_object into the backends). But this would need some discussion first, how to do this.

[vrishk]

Anything I can help with from my end?