Adapt different content type for the CAR format

[Gozala]

As @gobengo pointed out there is a application/vnd.ipld.car that is been used by IPFS gateways.

We should switch over to using that as content type.

[Gozala]

Note we should also figure out a way to do this without breaking existing clients that send requests and expect responses in application/car format.

[Gozala]

@gobengo on the related note we may also want to negotiate block encoding & hashing algorithm for the blocks inside the CARs. I was thinking using something like application/car+cbor, but sounds like that would not be a good idea. Do you know of a better way ?

[gobengo]

I was thinking using something like application/car+cbor

I think that's about as good as it gets in media types. 'structured syntax suffix'
Helpful backstory here:
https://www.rfc-editor.org/rfc/rfc6838.html#section-4.2.8

Do you know of a better way ?

Nope. It's line with things like application/ld+json.
Or this with multiple (but afaict there are not great exemplars for composing many suffixes like this) application/credential+ld+json

[gobengo]

I was thinking using something like application/car+cbor

Perhaps it should be {otherMediaType}+car e.g. application/cbor+car 🤔 (via @jonnycrunch here sort of)

[gobengo]

For our cases, application/vnd.ipld.car.json probably makes sense (when debugging an ipld.car response as car->dag-json)

[Gozala]

This got fixed in 7.0.0