It could happen that we unknowingly depend on a new version of a crate
without updating `Cargo.toml`. This could cause resolution issues for
downstream users. It's also unclear for outsiders to see which
dependencies we tested the crate with.
This change commits two lock files: `minimal` and `recent`. `minimal`
contains minimal depdendency versions, while `recent` contains
dependency versions at the time of making the change.
Further, this adds CI jobs to test with both lock files, CI job for
`internals` crate, removes old `serde` pinning and prints a warning if
`recent` is no longer up to date. (We may have to override it somehow if
any crate breaks MSRV.)
The documentation is also updated accordingly.
Co-developed-by: Tobin C. Harding <me@tobin.cc>
Closes#1230
Martin Habovstiak