Add is_valid_secp256_signature support

[ericnordelo]

Fixes #987

PR Checklist

• Tests
• Documentation
• Added entry to CHANGELOG.md
• Tried the feature on a public network

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 91.61%. Comparing base (9ad6d13) to head (b763c9f).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/account/src/utils/secp256_point.cairo	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1189      +/-   ##
==========================================
+ Coverage   91.57%   91.61%   +0.03%     
==========================================
  Files          47       47              
  Lines        1223     1228       +5     
==========================================
+ Hits         1120     1125       +5     
  Misses        103      103              

Files with missing lines	Coverage Δ
packages/account/src/eth_account.cairo	98.27% <ø> (ø)
packages/account/src/utils.cairo	87.50% <ø> (ø)
packages/account/src/utils/signature.cairo	87.50% <100.00%> (+4.16%)	⬆️
packages/testing/src/constants.cairo	100.00% <100.00%> (ø)
packages/testing/src/signing.cairo	100.00% <100.00%> (ø)
packages/account/src/utils/secp256_point.cairo	81.25% <85.71%> (ø)

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[immrsd]

Good job! Left a couple of minor comments

[immrsd]

parity could be represented by felt252 and x.high can be also converted to felt with into call. This way we could avoid having try_into and unwrap calls. What do you think?

[ericnordelo]

I tried to avoid it, but since y is a u256, to make parity a felt252 we would also need to .try_into().unwrap() y % 2. But we can make parity a u128 using y.low % 2 and also remove the .try_into().unwrap().

Updated!

[immrsd]

I was thinking about let parity: felt252 = y.low % 2 == 0 ? 0 : 1. But this solution also works since we've got rid of try_into!

[immrsd]

LGTM