Redact headers when exporting internal telemetry through OTLP

[jade-guiton-dd]

Description

Currently, when exporting the Collector's internal telemetry through OTLP, headers defined on the OTLP exporter will be marshaled in plain text when the Collector's configuration is exported (through the OpAMP extension, for instance). This PR adds a confmap.Marshaler implementation to the configuration structs which overwrites the header values with [REDACTED], as if the fields used configopaque.String (which would be hard to implement since they are defined in the external otelconf package).

To be honest I'm not super pleased with the dynamic way I implemented it in terms of performance, but I think it's the most reasonable way to implement it without adding too much complexity for something that should ideally be fixed at the otelconf level. It should also be adaptable to other cases where we need to redact marshaled configs after the fact, if necessary.

The changes to the existing test data were done to accommodate the new Marshal test (in some cases, assert.Equal will complain that a value isn't an untyped nil, but there is no way to produce one with our unmarshaling process), and to avoid making the input and output look unnecessarily different (e.g. for the capitalization of the verbosity levels).

Testing

I added some tests to otelconftelemetry/internal/migration which check the output of marshaling the configuration.

[codecov]

Codecov Report

❌ Patch coverage is 76.47059% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.22%. Comparing base (76ede07) to head (2351ad4).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...try/otelconftelemetry/internal/migration/v0.3.0.go	66.66%	3 Missing and 3 partials ⚠️
...try/otelconftelemetry/internal/migration/redact.go	87.50%	1 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (76.47%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14756      +/-   ##
==========================================
- Coverage   91.24%   91.22%   -0.02%     
==========================================
  Files         697      698       +1     
  Lines       44647    44681      +34     
==========================================
+ Hits        40738    40761      +23     
- Misses       2769     2775       +6     
- Partials     1140     1145       +5     

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[jade-guiton-dd]

The two failing tests seem to also be failing on main.

[evan-bradley]

I didn't deeply check which keys need to be redacted, but overall this looks good to me.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.