feat: add opt-in dataplane format

[github-vincent-miszczak]

Add an opt-in setting and the corresponding UI toggle to enable logs dataplane format.

Using this format allows Grafana correlations to work correctly with label values.
Without it, it's not possible to craft links that use label values when using Grafana correlations.

It's opt-in because the fields are renamed, which may break client-side transformations.

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Summary by cubic

Adds an opt-in setting to output logs in Grafana dataplane format, enabling automatic ${labelKey} variables in correlations. Default is off to avoid breaking transformations that reference Time/Line.

• New Features
  • New “Use dataplane format” toggle in datasource settings; provisioning key: jsonData.useDataplaneFormat.
  • When enabled: rename Time→timestamp and Line→body, and set frame meta to DataFrameType.LogLines with typeVersion [0,0] so ${labelKey} works in correlations.
  • Updated README, CHANGELOG, and tests to cover the new format.

^{Written for commit e49b2ea. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 8 files

[arturminchukov]

@github-vincent-miszczak Thanks for contributing! I didn't understand how it could help with the correlations. I'm just tried to set up a correlation but instead of Line field we just get the body field. I would be glad, if could share me a guide with setting up a correlation with a data plane format.

[github-vincent-miszczak]

Here is an example using the dataplane format without any transformation.
The link is correctly dynamically generated with our field value.

Label values get automagically promoted as top level variables.
Without this format, there is no syntax to access label values. At best we can workaround using transformation/regex, but that's not ideal.

[arturminchukov]

@github-vincent-miszczak Could you please sign your commits? Here, you can find a guide on how to do it.

[arturminchukov]

@github-vincent-miszczak
Right now, to use Grafana correlations (like linking from logs to traces), you have to enable the dataplane format. The problem is that it renames Time to timestamp and Line to body, which can break existing dashboards and panels that rely on those field names.

What I suggest: the plugin reads the correlation configs that the user has set up in Grafana, looks at which label field each correlation needs, pulls that value out of the log labels, and creates a clickable field for it — all at query time, automatically.

So the user just creates a correlation in the Grafana UI (say, logs → Tempo with trace_id), and it works. No need to enable any toggles, no field renaming, no risk of breaking anything.

To get the correlation configs at runtime, we use getCorrelationsService() from @grafana/runtime — specifically getCorrelationsBySourceUIDs([datasourceUid]) which returns all correlations where our datasource is
the source. Each correlation has a config.field telling us which label to extract.
What do you think?