Add a tendermint-validator crate

[tomtau]

fixes #1134

• Referenced an issue explaining the need for the change
• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests
• Added entry in .changelog/

[tomtau]

Thanks @tony-iqlusion ! Yes, tendermint-privval may be a better name.

As for the SignerProvider trait, I guess there are a few options:

1. use async_signature::Signer directly instead and require public keys as a separate explicit input argument to the privval service (this may be a bit more error-prone and one will find out any signer-related issues only after the first signing request arrives)
2. a new version of async_signature that will add public key retrieval functions and use that directly instead
3. change SignerProvider to take async_signature::Signer as a type parameter

What do you think?

[tony-iqlusion]

@tomtau for "public key retrieval", in cosmrs we use a helper trait with a blanket impl:

https://docs.rs/cosmrs/latest/cosmrs/crypto/secp256k1/trait.EcdsaSigner.html

Upstreaming something like this into signature/async-signature is something I've considered.

[codecov-commenter]

Codecov Report

Merging #1152 (97a0b92) into master (6a28510) will increase coverage by 1.0%.
The diff coverage is 86.0%.

@@           Coverage Diff            @@
##           master   #1152     +/-   ##
========================================
+ Coverage    64.7%   65.7%   +1.0%     
========================================
  Files         232     238      +6     
  Lines       15667   16210    +543     
========================================
+ Hits        10138   10664    +526     
- Misses       5529    5546     +17     

Impacted Files	Coverage Δ
privval/src/error.rs	0.0% <0.0%> (ø)
tendermint/src/signature.rs	54.9% <0.0%> (-5.1%)	⬇️
privval/src/config.rs	60.0% <60.0%> (ø)
privval/src/server.rs	84.8% <84.8%> (ø)
privval/src/state.rs	97.1% <97.1%> (ø)
privval/src/lib.rs	100.0% <100.0%> (ø)
privval/src/signer.rs	100.0% <100.0%> (ø)
tendermint/src/consensus/state.rs	99.4% <100.0%> (+10.0%)	⬆️
tendermint/src/private_key.rs	63.4% <100.0%> (+6.6%)	⬆️
tendermint/src/public_key.rs	75.2% <100.0%> (+0.2%)	⬆️
... and 15 more

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[tomtau]

@tony-iqlusion that's the third option and it seems good: if it's upstreamed into signature/async-signature in the future, it shouldn't be difficult to change. So, I switched SignerProvider to be a helper trait.

@thanethomson this PR should be good to go (sans some questions on the other PR: #1147 (comment) ) -- I could possibly add those signature trait implementations in #1147 if it's preferable to split it that way.

[tony-iqlusion]

Did a quick pass and this is looking good now!

I'll try to more thoroughly review this next week.

[tony-iqlusion]

@tomtau here's a PR to add a Keypair trait to the signature crate:

RustCrypto/traits#1080

It could have a corresponding AsyncKeypair trait in the async-signature crate.

[tony-iqlusion]

Added AsyncKeypair: https://docs.rs/async-signature/0.2.0/async_signature/trait.AsyncKeypair.html

[tony-iqlusion]

It seems this is blocked on #1225

[romac]

I switched the base branch from master to main so now this PR needs a rebase.

[tomtau]

I'm not sure when I'll get to this PR. Are you looking into merging it soon or is anyone interested in taking over it?

[romac]

No rush from our side, so feel free to come back to it whenever it suits you if you are still interested in getting this merged. And sorry for not being very reactive with this PR, we've had and still have limited capacity to work on tendermint-rs this past quarter.