Describe the bug
The Okta SSO identity manager implementation is not nearly as complete as the OneLogin identity manager, despite both being similar OAuth providers. For example, it cannot handle custom role mappings or users mapped to more than one role, unlike the OneLogin implementation.

Additionally, the current implementation of the Okta identity manager contains references to an invalid default role name, an incorrect default JWKS URL, and references org_id and org_realm which are not part of the AuthenticatedEntity class.

There are also no official docs on implementing the Okta SSO identity manager. The page https://docs.keephq.dev/deployment/authentication/okta-auth is missing, and the only reference to any required configuration is a single line in the table at the bottom of https://docs.keephq.dev/deployment/authentication/overview.

To Reproduce
Steps to reproduce the behavior:

1. Attempt to configure Okta SSO based on the existing identity manager and documentation

Expected behavior
Successful authentication with no further configuration other than what is specified in the documentation.

Additional context
I was able to locate some documentation in the original PR which added Okta support, but it does not appear this is in the official documentation anywhere: #5195

Upon further investigation it appears this is a regular Markdown file located at docs/authentication/okta.md but this does not appear to be the correct location for it.