Add validation for missing identifier in signing package

[natalieesk]

This closes #442

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.11% 🎉

Comparison is base (9b5d88d) 72.17% compared to head (d1fdfc7) 72.28%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #452      +/-   ##
==========================================
+ Coverage   72.17%   72.28%   +0.11%     
==========================================
  Files          30       30              
  Lines        2670     2681      +11     
==========================================
+ Hits         1927     1938      +11     
  Misses        743      743              

Files Changed	Coverage Δ
frost-core/src/error.rs	84.61% <ø> (ø)
frost-core/src/frost/round2.rs	91.01% <100.00%> (+1.26%)	⬆️

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[conradoplg]

Some comments but everything else looks great, love the test

[conradoplg]

Looks great!

Out of curiosity I measured performance and indeed we have a drop as expected, which gets diluted with more signers since it's a fixed amount of additional computation:

FROST Signing ristretto255/Round 2/2
                        time:   [143.11 µs 143.26 µs 143.40 µs]
                        change: [+48.619% +48.846% +49.075%] (p = 0.00 < 0.05)
                        Performance has regressed.
FROST Signing ristretto255/Round 2/7
                        time:   [225.57 µs 225.72 µs 225.88 µs]
                        change: [+25.906% +27.105% +28.724%] (p = 0.00 < 0.05)
                        Performance has regressed.
FROST Signing ristretto255/Round 2/67
                        time:   [1.2433 ms 1.2444 ms 1.2454 ms]
                        change: [+1.1933% +1.6641% +2.0133%] (p = 0.00 < 0.05)
                        Performance has regressed.

I'll create an issue to improve this later. Created #454