Guidance on undefined media types

[m-mohr]

Would love to see a more extensive, probably crowd-sourced list of what people are using for media types for different assets. https://github.com/radiantearth/stac-spec/blob/master/best-practices.md#common-media-types-in-stac is a nice start but obviously hardly scratches the surface of types.

Meanwhile, are their any guidelines for winging this? I'm not hopeful that we'll ever get registered MIME types for most of these (how long have we been waiting for parquet to get a MIME type??) I'm currently trying to document some vector objects that use flatgeobuf, and ESRI's shapefile and geodatabase formats; wondering if the GDAL driver names might provide a reasonable basis of reference: https://gdal.org/drivers/vector/index.html , e.g. application/x-<DRIVER SHORT NAME> maybe?

Or maybe that's a fools errand and we're better off omitting the type field and just providing a human-readable explanation of the file format using title or description fields?

Originally posted by @cboettig in #1203