[Metrics UI] Custom metrics in inventory don't survive navigation

[weltenwort]

Kibana version: master as of 78123a1

Original install method (e.g. download page, yum, from source, etc.): source

Describe the bug:

While the "default" view is selected on the inventory screen a custom metric is lost as soon as the user navigates anywhere, even within the same app. There is no warning about the loss of state.

Steps to reproduce:

1. Navigate to the inventory screen
2. Ensure that the current view is the "Default view"
3. Add a custom metric
4. Navigate to the settings screen
5. Navigate back to the inventory screen
6. Observe that the custom metric is not defined anymore

Expected behavior:

Either the custom metric is preserved or the user is warned when navigating away.

Note:

I created this in response to user feedback and the "expected behavior" is just my extrapolation from the wording of the feedback.

[elasticmachine]

Pinging @elastic/logs-metrics-ui (Team:logs-metrics-ui)

[roshan-elastic]

This is a valid issue, prioritising low until we decide to focus on Inventory again.

[elasticmachine]

Pinging @elastic/obs-ux-infra_services-team (Team:obs-ux-infra_services)

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[roshan-elastic]

Closing - we'll be superseding the existing inventory with a new one