`merlin` is currently a blocker for upgrading to `rand_core` v0.9 by way
of the `transcript.build_rng().finalize()` function (which we only pass
`ZeroRng` to).
There is an open PR to update `rand_core` in `merlin` and I have pinged
the relevant people to take a look, hopefully: zkcrypto/merlin#11
However, in the event we can't get `merlin` updated, this at least
unblocks the `rand_core` upgrade, and is being opened as a contingency
plan for that case.
The PR has been implemented in a way that it should be easy to switch
back to upstream `merlin` in the event they upgrade `rand_core`.
Like #582, there is a new release of `signature` (v2.2.0) which contains
no breaking changes from ed25519-dalek's perspective. The main notable
one is it bumps MSRV to 1.60, which so also happens to also be
ed25519-dalek's MSRV.
This commit loosens the version requirement to allow `>=2.0, <2.3` to
allow the `signature` 2.2 series.
The `signature` crate contains unstable, minor version-gated
functionality.
The v2.1 release did not change any of that, and only added new
functionality. So it's safe to relax the requirement for `signature` to
`>=2.0, <2.2`.
