Nest `CombineReferences` inside `WriteCombinedReferences`

[Charles Stern]

Working on #610 has me thinking about how to easily communicate common recipe styles. Over there, I'm centering on the idea that the basic version of all common pipeline styles should be expressible as: FilePattern | Opener | Writer. StoreToZarr fits this style, but our kerchunk recipes do not:

pangeo-forge-recipes/examples/feedstock/hrrr_kerchunk_concat_step.py

Lines 48 to 61 in f6af0e0

 | OpenWithKerchunk( 
     file_type=pattern.file_type, 
     remote_protocol=remote_protocol, 
     storage_options=storage_options, 
     kerchunk_open_kwargs={"filter": grib_filters}, 
 ) 
 | CombineReferences( 
     concat_dims=pattern.concat_dims, 
     identical_dims=identical_dims, 
     precombine_inputs=True, 
 ) 
 | WriteCombinedReference( 
     store_name="hrrr-concat-step", 
 ) 

To align kerchunk recipes with this style, we can nest CombineReferences inside WriteCombinedReferences, making the basic kerchunk recipe expressible as:

recipe = (
    beam.Create(pattern.items())
    | OpenWithKerchunk(...)
    | WriteCombinedReferences(...)
)

[Raphael Hagen]

This seems like a good call!

[Raphael Hagen]

Closed by #635