Add customer_ids support to mTLS context JWT

[sehkone]

Closes #770

[codecov]

Codecov Report

❌ Patch coverage is 93.87755% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.78%. Comparing base (5dab1ba) to head (6f61a5e).
⚠️ Report is 1 commits behind head on auth-mtls.

Files with missing lines	Patch %	Lines
src/lib.rs	50.00%	2 Missing ⚠️
src/auth/mtls.rs	97.77%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##           auth-mtls     #771      +/-   ##
=============================================
+ Coverage      73.74%   73.78%   +0.04%     
=============================================
  Files             71       71              
  Lines          18068    18103      +35     
=============================================
+ Hits           13324    13358      +34     
- Misses          4744     4745       +1     

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