Suggestion about Structuring a Composite "subject" Field

[evarga]

Background

The core specification lacks any recommendation how to cope with a composite subject field. Leaving everything to a producer may create an undesirable situation of packing, even semantically similar, subject content in arcane manner.

Proposed Changes

This PR adds an additional example, suggesting a different way to structure the content of the subject field, while fully preserving compatibility with the existing standard.

[duglin]

approved on the 2/29 call. Just waiting for one possible last minute tweak

[duglin]

thanks @evarga Merging