[BUG] notebooks not working with OpenSearch 2.17 (using cognito authentication)

[margussipria]

What is the bug?
Notebooks do not work after migrating from 2.15 to 2.17 with cognito security enabled (probably anything requiring cookies)

How can one reproduce the bug?

1. Go to '_dashboards/app/observability-notebooks#/'
2. See error (in console only)

core.entry.js:15 
 GET https://domain/_dashboards//api/observability/notebooks/savedNotebook 403 (Forbidden)

core.entry.js:15 Detected an unhandled Promise rejection.
TypeError: Cannot read properties of null (reading 'message')

What is the expected behavior?
saved notebooks should be loaded even with cognito security.

What is your host/environment?

• OS: Hosted OpenSearch_2_17_R20241112-P2 (latest)
• Version 2.17
• Plugins (defaults)

Do you have any additional context?
When opening notebooks after migration form version 2.15, notebooks are missing and session will die.

This is because ajax request /_dashboards/api/observability/notebooks/savedNotebook/ gets redirect response /_dashboards//api/observability/notebooks/savedNotebook (2 slashes and removed slash from end). during redirect cookies are not sent and response to redirect would be 403. Manually (with ALB) giving redirect url without 2 slashes results content returned correctly (cookies included).

There is 2 problems, original request is done to wrong URL and redirect is formatted wrongly. For calling of wrong route change was made at #1937.

route is https://github.com/opensearch-project/dashboards-observability/blob/main/server/routes/notebooks/noteRouter.ts#L278
and call is https://github.com/opensearch-project/dashboards-observability/blob/main/public/components/notebooks/components/main.tsx#L111 (probably also line 101)