Add error handling when the whole dashboard fails to load

Problem to solve

Provide users with feedback when the whole dashboard fails to load, for example with a network failure.

This is different to the current dashboard error handling on individual panels, which happens after the dashboard itself has loaded.

We should provide guidance to help the user troubleshoot / resolve the error.

Proposal

When a dashboard experiences a network error, ie it cannot be fetched from GraphQL, then add a page level error alert, with:

Something went wrong while loading the dashboard. Refresh the page to try again or see troubleshooting documentation.

Link to the troubleshooting section of the analytics dashboards help doc.

Implementation plan

frontend 2️⃣

• Catch errors from the GraphQl dashboard query, and show an error alert.
• Capture errors in Sentry (exclude network errors, as we cannot do anything to resolve these)