json array support for collectionFormat

[dtorok]

The spec lists several possible formats in the collectionFormat field for an array parameter.
My suggestion is to include json too because

• we use json everywhere, no need to introduce a new serialization format here
• json serializer is there already on both the client and server side
• it's as simple as csv (2 more bytes)

The swagger fragment would look like this:

        - name: id__in
          in: query
          required: false
          type: array
          collectionFormat: json
          items:
            type: integer
            format: int64

The URL would look like this:

https://example.com/api/users/?id__in=[1,2,3]

[mohsen1]

Are you proposing that items can be any JSON Schema also?

[webron]

We actually considered adding support for it around 2.0, but a substantial set of libraries that actually support this format.

[jharmn]

Link to parent #565

[fehguy]

This has been added by #804