Fix message for unknown API errors

[paescuj]

Scope

• Fix broken logic to get error message of unknown errors (e.g. from a Flow) for admin users
  • Brackets were missing, which resulted in the error object itself being used as the message
  • Example Flow Before After
• Clean-up of error handler
  • Wrap in async handler, similar to what we're using in other middleware/handlers - makes it easier to read and allows us to easily catch possible errors in the handler itself (unexpected, but would leak filesystem structure info if uncaught)
  • Add comments to reveal some of the magic happening here 🪄
  • Reusable fallback error
  • Prevent adding undefined extensions data / stack traces to error data (in dev mode)
  • Don't use toArray util to transform errors - would split string errors by commas
  • Better typing
• Shared InternalServerError

Potential Risks / Drawbacks

None

Review Notes / Questions

None

---

Fixes #22420, partially addresses #22416

[changeset-bot]

🦋 Changeset detected

Latest commit: 0e5a045

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@directus/api	Patch
@directus/errors	Minor
directus	Patch
@directus/extensions-registry	Patch
@directus/memory	Patch
@directus/validation	Patch

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[hanneskuettner]

One minor nitpick, otherwise it looks super clean