At https://github.com/n8n-io/n8n/pull/8213 we introduced Redis hashes
for workflow ownership and manual webhooks...
- to remove clutter from multiple related keys at the top level,
- to improve performance by preventing serializing-deserializing, and
- to guarantee atomicity during concurrent updates in multi-main setup.
Workflow activation errors can also benefit from this. Added test
coverage as well.
To test manually, create a workflow with a trigger with an invalid
credential, edit the workflow's `active` column to `true`, and restart.
The activation error should show as a red triangle on canvas and in the
workflow list.
