[Pkg-rust-maintainers] Bug#1020726: rust-log: please provide feature kv_unstable_serde

[Peter Green]

> Please provide feature kv_unstable_serde, needed for packages I am
> preparing for Debian.

This requires the serde feature in value-bag to be enabled, which
in turn requires sval and serde_fmt

sval is currently in NEw https://ftp-master.debian.org/new/rust-sval_1.0.0~alpha.5-1.html

I don't see any evidence that anyone is currently working on serde_fmt