add casbin user test

[kradalby]

Updates #2333

[ghost]

Pull Request Revisions

Revision	Description
r3	Improved OIDC claims identifier generation Added URL path joining for OIDC claims identifier when issuer starts with "http", with fallback to previous method
r2	Removed extra slash in URL Fixed OIDC provider identifier URL by removing an extra forward slash in the test case configuration
r1	Added OIDC claims test case Expanded users_test.go with a new test case for OIDC claims parsing, covering a specific GitHub issue scenario

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✅ AI review completed for r3

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[ghost]

There appears to be a double slash in the ProviderIdentifier URL string: https://oidc.example.com//xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. Is this intentional or should it be a single slash after the domain?