Allow and document how users control SE tracing for OpenTelemetry using Helidon config under tracing (and telemetry)

[tjquinno]

Description

Resolves #10790

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NOTE: Changed to a draft PR. The PR will also involve some coding changes, not just doc. The description below still describes doc-only changes. Updates to the changed files and the description coming soon.

Our SE tracing page contains details about using and configuring Jaeger and Zipkin tracing but not OpenTelemetry. Our code does not currently support using the tracing config block if the project uses the Helidon OpenTelemetry tracing provider.

This doc PR allows users to use the tracing config block adds to that page some dependency and config information.

Note that the doc directs users choosing the OpenTelemetry tracing provider to use the recently-added telemetry configuration feature, not the tracing config section.

This is because the existing code does not support preparing OpenTelemetry using the tracing config section, and that is because:

• Using the telemetry section is a far more functional approach.
• We would have to change Helidon code to allow users to use tracing config settings to control OpenTelemetry. Although that would provide superficial consistency with the other tracing providers (Jaeger and Zipkin), doing so would introduce problems:
  • It would be less functional than using telemetry.
  • It would be confusing to have two ways of configuring essentially the same behavior.
  • Changing the code could change the way existing apps behave if they use the OTel TracerProvider.Builder programmatically or assign settings in the tracing config section, which the current code almost completely ignores.

Note also that this PR does not change how users configure OTel behavior using MP. That is still done according to the MP Telemetry spec and not using our telemetry settings.

Documentation

This is a doc PR.

[tjquinno]

After a discussion with other team members I'm enlarging the scope of the PR a bit beyond just doc. So I've marked it as a draft.