Support named handlers #156

[treivize]

I guess named handlers are managed as expected with a defaulting for any config property to the root splunk configuration.

I was a bit sad about having had to duplicate the properties from the root level and the named handler ones, but I did not find how to customize the default value to detect in the recorder when to fetch the root value or the handler value when a default value is defined upfront. Any idea?

Fixes #156

[treivize]

Finally, as discussed with @rquinio1A, the config at named handler level will not default on the root level, but will be handled independently only reusing the root level defaulting values.

There is no more config property duplications now.

[rquinio1A]

Finally, as discussed with @rquinio1A, the config at named handler level will not default on the root level, but will be handled independently only reusing the root level defaulting values.

There is no more config property duplications now.

It could indeed have been interesting that named handlers inherit their configuration from the root/default handler.
However we've seen that:

• For fields, you can't differentiate a default value from @ConfigItem annotation vs explict configuration of the user using the default value, so you don't know whether root handler config should be used...
• Quarkus built-in handlers (file, console, ...) don't seem to do this, so it could be confusing for users

[rquinio1A]

There's the generated config included in the doc, but it could you add a small doc section under features (https://github.com/quarkiverse/quarkus-logging-splunk/blob/main/docs/modules/ROOT/pages/index.adoc#features) with an example config and typical code usage like in the unit test ?
Few points to highlights:

• Every handler is isolated and uses a separate Splunk client and connection pool, which means it has a cost.
• The configuration from the root handler are not inherited by named handlers.
• `quarkus.log.category."named-handler".use-parent-handlers=false is required if you do not want the root handler to also receive log events already sent to named handlers.

[rquinio1A]

@treivize Thanks for the contribution!