Do not rely on controller storage

[sed-i]

Enhancement Proposal

We need to drop use_juju_for_storage=True because controller storage is deprecated.

grafana-k8s-operator/src/charm.py

Line 1312 in c65b326

main(GrafanaCharm, use_juju_for_storage=True)

Need to figure out how to go about dashboards and sources relations on upgrade-charm.

grafana-k8s-operator/lib/charms/grafana_k8s/v0/grafana_dashboard.py

Line 1310 in c65b326

self._stored.set_default(dashboards={}) # type: ignore

grafana-k8s-operator/lib/charms/grafana_k8s/v0/grafana_source.py

Lines 503 to 506 in c65b326

	self._stored.set_default( # type: ignore
	sources={},
	sources_to_delete=set(),
	)

[lucabello]

We need to find a solution for dashboard and sources; we should probably store those in a PVC, but how do we do that?

The only other alternative would be a peer relation, but (other than being a hacky solution) we would probably hit size limitations when storing all the dashboards.