Add parameters for top-level request body properties

[sethmlarson]

Inspired by @ezimuel I'd like to add named body parameters where possible while preserving the ability to call body=... in the free-form body cases.

• Adds names to bodies that are scalars or arrays and define x-codegen-request-body-name
• Adds required parameters which map to the JSON body
• Allows users to continue to use body if there is any optional parameters or if the body is completely freeform (like put_schema())
• If there's a conflict between path and body parameters we give up and only allow free-form body for now
• If there's a conflict between query and body parameters we favor body parameters to avoid putting too much in query string, although this case is rare.

Also while working on this found that WorkplaceSearch.indexDocuments spec likely should have x-codegen-request-body-name equal to documents to match AppSearch.indexDocuments parameter name.

[sethmlarson]

This construction gets a lot more complex with request body parameters but hopefully the comments make things easier to follow.

[ezimuel]

Maybe you can write an example case?

[sethmlarson]

If there's more than one body parameter we are called body

[sethmlarson]

Not doing anything with structured responses yet so deleting this for now. However structured responses can be directly added on to what we have without it being a breaking change (since structured responses will still be accessible like a dict/list)

[sethmlarson]

There's some reference loops within requestBody schemas that needs resolving, for now this is an easy way to ensure we resolve all $ref instances as far as we need without writing a "better" ref resolver.

[ezimuel]

Do you want to prevent circular reference in $ref? I found this comment about circular ref in OpenAPI.

[ezimuel]

The only point that I raise is about the possible naming conflict between params, body and query. This is because you are passing everything in the constructor, right? Maybe you can define an alternative way, for instance leaving the body as is and providing a builder class to create the body using parameters.