Add catalog_dict examples

[charlesbluca]

Adds two implementations of GFDL CM2.6's esm collection, based on our two ideas for handling internal catalog_dicts:

• Have all entries in an array under an attribute called esm:catalog
• Have all entries in assets with their own unique key

[charlesbluca]

Thanks for the review! I'll commit these changes and do the same with sample-catalog-dict-attribute.json.

[m-mohr]

Great, both files validate now.

[charlesbluca]

In examples/sample-catalog-dict-attribute.json, should "esm.data_column_name" be changed to "esm:data_field"?

[m-mohr]

Hmm, there's no such field in my schema. And also I'm wondering why there's a "esm:catalog". That should be in the assets, I think? Like in the other example...

[charlesbluca]

Originally the intent of my examples was to showcase how a single-file catalog might look if we took either approach we were discussing on call - either each item would be given a key and placed in assets or all items would be enumerated in a JSON dictionary, hence the esm:catalog attribute.

If the schema only supports entries in assets, I'm happy to remove the incorrect example!

[m-mohr]

Maybe we should wait for the written spec and then discuss based on that and the schema. I may not have everything right with the schema, too. But I thought we had discussed to put the esm:catalog parts into assets. Who was the person working on the written spec again? @jhamman?

[rabernat]

Narrative description is here: https://github.com/NCAR/esm-collection-spec/blob/stac/collection-spec/collection-spec.md

[andersy005]

I am curious about how to specify esm:format and esm:data_field fields

 "esm:data_field": "path",
 "esm:format": "zarr"

for catalogs that are embedded in the JSON file? Where do these fields belong?

[m-mohr]

It seems the self-contained catalogs need a discussion. They are not in the Schema yet, partly described in the documentation and in these examples, but the final behavior seems not clear yet.