otlp: mention service.name in kitchen sink cfg doc - closes #475

[clux]

adds a possibly slightly more useful key/value combination for docs.

it's probably a common thing to want to set, even if it's not a thing that otel cares about.

[TommyCpp]

May need to do the same change in README?

[clux]

Done.

Btw would you accept PR for adding OtlpPipelineBuilder::with_service_name like in opentelemetry-jaeger?
Might cater to the common use case a bit more ergonomically.

[TommyCpp]

Btw would you accept PR for adding OtlpPipelineBuilder::with_service_name like in opentelemetry-jaeger?
Might cater to the common use case a bit more ergonomically.

Hmm, I guess the problem here is OTLP still doesn't have the service.name concept, with_service_name would be confusing if users are using a backend that doesn't recognize the service.name resource. But maybe we should make a note in the doc to explain if the backend recognizes a Jaeger-style service name, we can set it via resource.