Add Failure API tests for user defined federated authenticator management

[Shenali-SJ]

Proposed changes in this pull request

This PR adds API tests to validate failure scenarios for IdPs with user-defined authenticators.

Related Issue:

• Provide API for the new custom authentication management #21216

Related PR:

• [Draft] Add integration tests for managing user defined federated authenticator #21646

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Checklist (for reviewing)

General

• Is this PR explained thoroughly? All code changes must be accounted for in the PR description.
• Is the PR labeled correctly?

Functionality

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• Does the UI work as expected? There should be no Javascript errors in the console; all resources should load. There should be no unexpected errors. Deliberately try to break the feature to find out if there are corner cases that are not handled.

Code

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• Does the PR introduce any inefficient database requests? Use the debug server to check for duplicate requests.
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Tests

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• If this is a bug fix, are tests for the issue in place? There must be a test case for the bug to ensure the issue won’t regress. Make sure that the tests break without the new code to fix the issue.
• If this is a new feature or a significant change to an existing feature? has the manual testing spreadsheet been updated with instructions for manual testing?

Security

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• Are all UI and API inputs run through forms or serializers?
• Are all external inputs validated and sanitized appropriately?
• Does all branching logic have a default case?
• Does this solution handle outliers and edge cases gracefully?
• Are all external communications secured and restricted to SSL?

Documentation

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• Are changes to the API documented in the API docs? If this PR introduces new API functionality or changes existing ones, the changes must be documented.
• Are reusable components documented? If this PR introduces components that are relevant to other developers (for instance a mixin for a view or a generic form) they should be documented in the Wiki.