Introductory text

[romaintailhurat]

The API swagger specification introductory text needs to be clear that the target DDI product is Lifecycle.

[NicoLaval]

Today we only expose DDI-L 3.3, via Accept media types like application/vnd.ddi.structure+json;version=3.3 (and the XML twin).

Is "structure" mean Lifecycle?

Later, we certainly want DDI-C, DDI-L and DDI-CDI, with version choice.

Open question: is one vendor MIME type per product (plus a version parameter) enough, or do we also need product/version in the URL path? I need to check how DDI media types are defined/used before locking that in.

I'll at least update the Swagger intro soon so current scope is clear.