v3.2: Enc style defaults

[handrews]

While working on cookie-related style changes, I noticed that we are unclear on how style defaulting works for the Encoding Object. Specifically, in 3.1.1 we clarified that all of style, explode, and allowReserved apply when any of those three are explicitly present. Otherwise, contentType applies (even if it is absent- its defaults apply).

So the default behavior for style takes place if either of the other two fields are there, but not if none of them are there (whether contentType is there or not).
This requires some rather complex schema changes and tests, which have not been done yet.

On the one hand, this is a clarification and should probably be backported to 3.1.2. On the other hand, it has schema changes, but more in the "we got the schema wrong" sense than in the "we're changing what was expected." I'm not entirely sure what to do with this for 3.1.2.

• schema changes are included in this pull request
• schema changes are needed for this pull request but not done yet
• no schema changes are needed for this pull request

[lornajane]

Helpful clarification, thanks.

[karenetheridge]

I've got a schema change for this, but I don't see how it can be tested, since "default" is an annotation-only keyword and its presence or absence cannot cause a validation failure.

[handrews]

@karenetheridge I would not expect a test is necessary- does the coverage go down in a way that makes things fail when you add the schema change? If not, at least for right now I think that's sufficient. Testing default is really impossible (as you know but others might not) because it's an annotation that only applies when the instance is not there to be annotated 🤦