Expose the dashboard transformation logic as a script

[lucabello]

Could we stop forcing carrying over diffs for COS? I mean forking upstream dashboards to have Juju specific variables like $juju_model, $juju_model_uuid, $juju_application, $juju_unit makes sense to give a better visibility of Juju models. However, carrying over the diff just to replace a variable (${DS_PROMETHEUS} -> ${prometheusds}, $datasource -> ${prometheusds}) doesn't make much sense to me.

I don't think we have that option, unfortunately. If this isn't done, and there is no datasource in Grafana named whatever upstream expects it to be named, the dashboard won't work once Grafana loads it as nothing is available to load the data.

We try to identify datasources and replace them with the prometheus and loki charm datasources, but this isn't fool proof, which is why we ask the charm authors to name them correctly from the get-go.

Originally posted by @simskij in #274 (comment)

[lucabello]

Closing this as we don't see it being useful!