Spike: users can't see failures in integrations with third parties

For example: https://github.com/Flagsmith/flagsmith/issues/7350 — unless they notice it otherwise, the user would never know [how] Flagsmith is failing to send events to Grafana.

For any other integration that connects to third parties, we do not expose failures to the user.

One suggestion is to add an "Integration log" tool from the integrations list, that allows the user to see the list of requests made, and their responses, or at least their headers. For reference: Sentry provides this "Audit log" tab in webhook settings for its Feature Flag change tracking tool.

(sadly I could produce no events for the above screenshot)

## Acceptance criteria

Pending spike / RFC.

- [ ] Users can see how an integration they configured is failing.
- [ ] Integration errors originated by 2nd or 3rd-party issues do not crash the app — i.e. won't go to Sentry.