Common: make vendor behavior consistent

[chuwy]

Several applications group schemas by vendor field, but there's two different behaviours.

1. com.acme.marketing-schemas are subset of com.acme
2. com.acme.marketing is independent of com.acme

I believe first behavior is correct. The whole point of vendor is to provide proper namespacing and namespacing assumes hierarchy.

• Documentation
• Scala Iglu Client
• Scala Repo Server
• (probably) Schema DDL

[alexanderdean]

Can you be specific about what you mean by "behaviours" - what is done differently within these 3-4 applications based on differing treatments of the vendor field?