Fix missing resource in logs, fix custom batch callback & make batches configurable

[TheTeaCat]

• Fixes missing resource in logs
• Fixes custom batch callback not being used when set
• Makes max batch size and log age configurable

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 84.08%. Comparing base (5160c3f) to head (481a74d).

Files	Patch %	Lines
middlewares/http/middleware.go	72.72%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev      #37      +/-   ##
==========================================
- Coverage   84.34%   84.08%   -0.26%     
==========================================
  Files           8        8              
  Lines         543      553      +10     
==========================================
+ Hits          458      465       +7     
- Misses         73       75       +2     
- Partials       12       13       +1     

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