Backport of UI: Test business logic for oidc callback params into release/1.11.x

[hc-github-team-secure-vault-core]

Backport

This PR is auto-generated from #19727 to be assessed for backporting due to the inclusion of the label backport/1.11.x.

WARNING automatic cherry-pick of commits failed. Commits will require human attention.

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The below text is copied from the body of the original PR.

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This PR moves the logic that happens in beforeModel for the oidc callback route into an easily-testable method.

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Overview of commits

• 61b152c

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