fix: null-checks and empty-strings

[eledhwen]

• adding null-checks on null ids during component build
• mapping user-provided null metric tags entries to empty strings for micrometer Tag compatibility
• switching test logging backend from simple-logger to logback

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 55.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 82.20%. Comparing base (e7178de) to head (86e45a2).

Files with missing lines	Patch %	Lines
...lluin/pipeline/builder/PayloadPipelineBuilder.java	0.00%	1 Missing and 1 partial ⚠️
.../input/initializer/builder/InitializerBuilder.java	50.00%	1 Missing and 1 partial ⚠️
...tech/illuin/pipeline/sink/builder/SinkBuilder.java	50.00%	1 Missing and 1 partial ⚠️
...tech/illuin/pipeline/step/builder/StepBuilder.java	50.00%	1 Missing and 1 partial ⚠️
.../tech/illuin/pipeline/metering/tag/MetricTags.java	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #123      +/-   ##
============================================
- Coverage     82.52%   82.20%   -0.32%     
- Complexity      765      769       +4     
============================================
  Files           137      137              
  Lines          1951     1967      +16     
  Branches        116      117       +1     
============================================
+ Hits           1610     1617       +7     
- Misses          267      271       +4     
- Partials         74       79       +5     

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[victor-illuin]

Ok for me.

[theo-malka]

Ok pour moi, modulo la question sur le changement de logger.