Draft: Automatically redirect users to SAML IdP on session timeout

What does this MR do?

We implemented the 7-day timeout for SAML groups for GitLab.com which requires users to re-auth into their SAML provider. This requires users to click to trigger a SAML log-in to check if they still have access to their IdP. This isn't the best user experience.

This improves the experience by making a request out to the SAML provider when the 7-day limit has expired and not require a user click to do so. This is a common pattern used in other enterprise applications.

Related to #292811 (closed)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team