Missing many types from hyper_old_types::header

[jplatte]

I noticed the self_update crate is pulling in a bunch of outdated dependencies through hyper_old_types, but uses only its typed headers for LinkValue and RelationType. I attempted to switch out hyper_old_types for headers, but found that these aren't defined here currently. Have they been removed intentionally or is this crate more of a from-ground rewrite than an extraction of the old typed header from hyper and only needs a PR to add these?

[seanmonstar]

is this crate more of a from-ground rewrite than an extraction of the old typed header from hyper and only needs a PR to add these?

Mostly this. One goal of this crate was to fix some mistakes with hyper's older typed headers: too many internal details were publicly exposed (structs with all fields public). Ideally this crate could add typed headers in a way where their details aren't exposed, so we can make optimizations or what-have-you without it being a breaking change.