http_range: Parse Range strings with length

[sudhirj]

Description

gotd's http_range does not currently parse range headers of the form

content-range: bytes 100-200/1048576000

that come from 206 partial responses. Are we interested in a separate method that parses these? I can write one up.

References

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Range - even the first example there isn't parsed by http_range right now.