refget: v2 spec for Range header errors does not align with typical usage

Creating on behalf of @davidlougheed as the GitHub issue transfer code wasn't working for me.

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For range headers, it is [generally accepted](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/416) that the `Range Not Satisfiable` error is to be used if a "document doesn't contain such ranges".

In Refget v2, `400 Bad Request` is used for this instead; I believe a 416 would be better because it can then require a [Content-Range](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Range) response header with the total sequence length, allowing clients to subsequently discover valid range queries that can be made and aligning better with the original intent of HTTP range responses.