Clarify losslessness requirements in json-ld handling

[arnoweiss]

Feature Request

With the move to make json-schemas normative, it's necessary that the exact requirements for adding non-DSP-native properties are clear. Participants need to extend messages in such a manner that neither processing as json or json-ld lead to different outcomes.

Which Areas Would Be Affected?

There should be an additional section on payload handling, similar to the DCP. However, to achieve interop between json-ld- and non-json-ld-aware applications, I expect there may a need to mandate adding resolvable remote context objects containing the json-ld term extending the DSP messages.

normative

Why Is the Feature Desired?

safety in during processing and API usage. see #55 (comment)

Solution Proposal

Clear commitment for or against losslessness with ensuing mandates on client behavior.

[arnoweiss]

should be picked up after closing #66