[dashboard] fix invalid dashboard displayed as 404 instead of showing validation error

[nreese]

Closes #211659

PR updates loadDashboardState to throw content management error when status is not a 404. PR does not attempt to clean-up DashboardRenderer's display of the error.

test instructions

1. use saved object import to import dashboard with schema errors - https://github.com/elastic/kibana/blob/main/x-pack/test/functional/apps/dashboard/group2/migration_smoke_tests/exports/lens_dashboard_migration_test_7_12_1.ndjson.
2. open dashboard, verify schema validation error is displayed.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[nreese]

@elasticmachine merge upstream

[ThomThomson]

Hey @elastic/ax-design folks! Would someone mind taking a look at a quick design for a generic non-404 Dashboard load error? Right now we're just pushing the raw error text - but a simple upgrade would be to render an empty page error component with a simple title and the full error message. Would that be sufficient?

[andreadelrio]

Hey @elastic/ax-design folks! Would someone mind taking a look at a quick design for a generic non-404 Dashboard load error? Right now we're just pushing the raw error text - but a simple upgrade would be to render an empty page error component with a simple title and the full error message. Would that be sufficient?

@ThomThomson Yes, a simple EuiEmptyPrompt would do it. If we want to keep the implementation simple we can simply pass an icon to it (as opposed to an illustration). @florent-leborgne should we able to help us with the copy. Would it be possible to offer a recovery action in a button? if so we can include it.

<EuiEmptyPrompt
  iconType="error"
  iconColor="danger"
  title={<h2>Unable to load dashboard</h2>}
body={<p>Some details go here.</p>}
actions={
<EuiButton color="primary" fill>
  Some action we can offer you
</EuiButton>
}
/>

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 83406f5

Failed CI Steps

• FTR Configs #105

Test Failures

• [job] [logs] FTR Configs #105 / Cloud Security Posture Vulnerabilities Page - DataTable "before all" hook in "Vulnerabilities Page - DataTable"

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
dashboard	549.8KB	550.2KB	+414.0B

History

• 💔 Build #277489 failed 69bcab8
• 💔 Build #277479 failed 93cadbe

[kibanamachine]

Starting backport for target branches: 8.19

https://github.com/elastic/kibana/actions/runs/14891723430

[kibanamachine]

💚 All backports created successfully

Status	Branch	Result
✅	8.19

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