Extend message attribute handling

[martincostello]

Handle message attributes of type Number or with a custom suffix label.

Resolves #1556.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.36%. Comparing base (56b8877) to head (dcbbec2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...aging/MessageSerialization/NewtonsoftSerializer.cs	84.61%	1 Missing and 1 partial ⚠️
...ing/MessageSerialization/MessageAttributeParser.cs	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1557      +/-   ##
==========================================
- Coverage   78.65%   78.36%   -0.29%     
==========================================
  Files         140      141       +1     
  Lines        3556     3550       -6     
  Branches      501      501              
==========================================
- Hits         2797     2782      -15     
- Misses        511      519       +8     
- Partials      248      249       +1     

Flag	Coverage Δ
linux	78.36% <87.50%> (-0.29%)	⬇️
macos	?
windows	47.35% <87.50%> (+0.89%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.