Open io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender in the library for extension / customisation

[oren101ways]

Is your feature request related to a problem? Please describe.

New Relic have a max length on attributes, and as such long stack traces are getting truncated.

We would like to customise the stack traces (filter lines, limit number of lines, root cause first etc)

Describe the solution you'd like

OpenTelemetryAppender is using LoggingEventMapper internally to omit events. Both classes are completely closed to extensions.

1. Allow extension of LoggingEventMapper
2. Add Function<Throwable,String> to LoggingEventMapper.Builder (as default extract current implementation of setThrowable)
3. change LoggingEventMapper.setThrowable to call the new function: attributes.put(SemanticAttributes.EXCEPTION_STACKTRACE, stacktraceConverter.apply(throwable));
4. Enable OpenTelemetryAppender configuration, for example:
   overload install method with instance of LoggingEventMapper
   overload start method with instance of LoggingEventMapper

Describe alternatives you've considered

The only alternative is to copy the code of OpenTelemetryAppender and LoggingEventMapper and change it as needed

Additional context

No response

[trask]

sounds a bit similar to open-telemetry/opentelemetry-java#4162 (but applied to log-based exceptions as opposed to span event based exceptions)