adr: dashboard collision

[lucabello]

We should update our dashboard best practices with the outcome of this ADR.

Related:

• https://github.com/canonical/grafana-k8s-operator/issues/342
• https://github.com/canonical/grafana-k8s-operator/issues/271
• https://github.com/grafana/grafana/issues/78908

[sed-i]

@lucabello just for reference, could you mention the length and charset limits for title, uid?