[oas3] base64 vs byte

The spec makes numerous references to {format: base64} (here and here for example). However this format is not defined in either the wright-00 JSON-schema spec, nor in the OAS3 defined data types.

[handrews]

In OAS 3.1, this can now be handled properly from the JSON Schema perspective. Specifically:

type: string
contentEncoding: base64

is a base64-endcode string (where base64 is per RFC 4648). You can use any RFC 4648 or RFC 2045 encoding, so base64url or quoted-printable are also valid.

If you are encoding a specific media type, such as a PNG file:

type: string
contentEncoding: base64
contentMediaType: image/png

Note that the content* keywords are informational, and are not validated during JSON Schema validation.

For binary transfer, use

type: string
contentMediaType: application/octet-stream

or some other media type.

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we should probably deprecate "format": "base64" and "format": "binary" in OAS 3.1 although I don’t feel strongly about it. Well… I have lots of strong feelings about format but that’s a rant for another time.

[jwalton]

FWIW, my vote is for base64. It much more clearly conveys the intent.