feat: Add logging custom attributes

[yahmed153]

Links

https://new-relic.atlassian.net/browse/NR-354877

Details

Added Custom Attributes via environment variable NEW_RELIC_APPLICATION_LOGGING_FORWARDING_CUSTOM_ATTRIBUTES or programmatically. Format of key/value is key1:val1;key2:val2;....

[yahmed153]

TODO: Add link to docs like Labels

[Newrelic-Boomi]

https://new-relic.atlassian.net/browse/NR-423812

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.40%. Comparing base (58fb0b0) to head (9790046).
Report is 33 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #1041       +/-   ##
============================================
+ Coverage    63.73%   77.40%   +13.66%     
============================================
  Files          217      113      -104     
  Lines        17921    12702     -5219     
============================================
- Hits         11422     9832     -1590     
+ Misses        6075     2539     -3536     
+ Partials       424      331       -93     

see 330 files with indirect coverage changes

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[yahmed153]

@nr-swilloughby would we need to add CustomAttributes to this struct

[yahmed153]

Creating PRs for AgentSpec and DocsSite as well

DocSIte PR

[nr-swilloughby]

@nr-swilloughby would we need to add CustomAttributes to this struct

I don't think we necessarily do, but that's a good question. We don't normally add things there for every feature we add. The items there are specifically the values that show up at the top level of the configuration values for the agent's connect payload, and are extracted from the Config struct. However, as you can see the entire Config struct is also included as the settings value of that data structure itself anyway, so your values are already in there automatically, just deeper down inside the struct. So unless there's a specific reason to bring a value up to the top level, we don't need to do anything and they'll just show up in the general settings value.