Content Range unit for RFC 7233 compliance

[Oquile]

The Content Range response HTTP header is missing a unit declaration. It should be in the form :
Content-Range: <unit> <range-start>-<range-end>/<size>

Supplementary docs-
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Range
https://httpwg.org/specs/rfc7233.html#header.content-range

This change also makes PostgREST compatible with Varnish HTTP Cache (https://varnish-cache.org/).

[Oquile]

This breaks build and tests. Will close and re-roll another

[steve-chavez]

This change also makes PostgREST compatible with Varnish HTTP Cache (https://varnish-cache.org/).

@Oquile Definitely something we want, the lack of range-unit was also reported in #1089.

[steve-chavez]

@Oquile You still interested in this one? Since it's a breaking change I'd be better to merge it now, I'll be doing a new release later today.

[steve-chavez]

Seeing #1089 (comment), I think we should go with items instead of bytes for our <range-unit>.

There's also a Content-Range: rows.. I found in the wild but I don't think the name matters as much, let's go with the most common one(which seems to be items).

[Oquile]

@steve-chavez - It is (currently!) beyond my ablity to do a succesfully patch for this quickly.

[wolfgangwalther]

Since it's a breaking change I'd be better to merge it now, I'll be doing a new release later today.

I think it would be better to be able to discuss breaking changes - and not have a workflow of doing them and then releasing immediately.

If you want to make a release soon, this should not go in.

[steve-chavez]

It is (currently!) beyond my ablity to do a succesfully patch for this quickly.

No problem! Seemed like a simple fix so I gave it a try on #2204.. I bet it breaks a lot of tests though.

If you want to make a release soon, this should not go in.

Bummer, this seems like something in need of a fix for quite a while now.