Allow extra_fields in Column

[martinfleis]

Hi,

thanks for this extension! I would like to store a bit more details for some columns than name, description, and type. I can technically do that already but I guess that doing so would violate the spec. Can we include an extra_fields option, similarly to the one in providers?

[TomAugspurger]

I think that JSON schema allows for arbitrary additional fields on any object. They just don't get validated. I think that pystac uses extra_fields for stuff that isn't necessarily from an extension.

So you're certainly free to store additional information there. But if you think it'd be generally useful then it'd make sense to standardize it as an optional field here.

[ankostis]

Some extra fields to consider (and hopefully STAC Browser to be able to search):

• tags: arbitrary text
  -labels (hierarchical tags with some delimiter eg foo.bar)

[feefladder]

Additional extra field:
License
For example, if some columns are considered sensitive data, they would have a proprietary license, whereas the other columns would have an open license. The example I am working on now is in-situ measurements, of which the location can be considered sensitive.