Improve documentation on the usage of io.quarkus.logging.Log in extensions

[mcruzdev]

Description:

The current Quarkus documentation suggests using Log only in application classes, not in external dependencies. However, Log can work in extension modules if they have a Jandex index, although this behavior might not be reliable.

The documentation doesn’t mention that:

• The stack walk fallback in logging can cause performance issues.
• Extensions should use standard loggers like Logger.getLogger() instead of Log.

[mcruzdev]

cc: @SergioRuyDev do you like to add it?

[Ladicek]

The stack walk fallback in logging can cause performance issues

That's because that is only supposed to be triggered in test. It doesn't apply to prod mode, where performance is important.

[quarkus-bot]

/cc @MichalMaler (documentation), @ebullient (documentation), @inoxx03 (documentation), @michelle-purcell (documentation), @rolfedh (documentation), @sheilamjones (documentation), @sunayna15 (documentation)