Dynamic topic for googlecloudpubsub exporter

[JakubDaleki]

Component(s)

exporter/googlecloudpubsub

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

Different logs (for example from different files) should be written to different topics on GCP PubSub. Current implementation allows only to specify one destination topic in static yaml config.

Describe the solution you'd like

I want to add a new flag to config topic_from_attribute. If set to true each log should be sent to a topic specified in Attribute gcp.topic of a LogRecord. If attribute is not present or is in invalid format logs should be sent to default topic specified in the topic field.

My PR showing changes needed to obtain this mechanism: https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/33545/files

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• exporter/googlecloudpubsub: @alexvanboxel

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