feat: add custom claim enricher

[loekensgard]

I have implemented an enricher designed to accept a custom claim as an input. This enricher will enrich the logs with the specified property if the custom claim is present.

[codecov]

Codecov Report

Attention: Patch coverage is 97.56098% with 1 line in your changes missing coverage. Please review.

Project coverage is 98.26%. Comparing base (376966d) to head (40a4b14).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
...erilog.Enrichers.Claims/Enrichers/ClaimEnricher.cs	97.22%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #12      +/-   ##
==========================================
- Coverage   98.64%   98.26%   -0.39%     
==========================================
  Files           7        9       +2     
  Lines          74      115      +41     
  Branches        5       11       +6     
==========================================
+ Hits           73      113      +40     
- Partials        1        2       +1     

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[h3rmanj]

LGTM!