95245 refactor new confirmation page tests and add more

[christinec-fftc]

Are you removing, renaming or moving a folder in this PR?

• [x] No, I'm not changing any folders (skip to TeamSites and delete the rest of this section)
• [ ] Yes, I'm removing, renaming or moving a folder

Did you change site-wide styles, platform utilities or other infrastructure?

• [x] No
• [ ] Yes, and I used the proxy-rewrite steps to test the injected header scenario

Summary

• Refactor new confirmation page unit tests to make them reusable, and add error scenarios

team: @department-of-veterans-affairs/dbex-trex toggle cleanup: https://github.com/department-of-veterans-affairs/va.gov-team/issues/95247

Related issue(s)

department-of-veterans-affairs/va.gov-team#95245

Testing done

• Manual tests to verify expected behavior when non 200 errors occur (see info in ticket), added unit tests

Screenshots

n/a

What areas of the site does it impact?

526ez submission flow

Acceptance criteria

Quality Assurance & Testing

• [x] I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• [x] No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• [x] Linting warnings have been addressed
• [ ] Documentation has been updated (link to documentation *if necessary)
• [ ] Screenshot of the developed feature is added
• [ ] Accessibility testing has been performed

Error Handling

• [ ] Browser console contains no warnings or errors.
• [ ] Events are being sent to the appropriate logging solution
• [ ] Feature/bug has a monitor built into Datadog or Grafana (if applicable)

Authentication

• [ ] Did you login to a local build and verify all authenticated routes work as expected with a test user

Requested Feedback

(OPTIONAL) What should the reviewers know in addition to the above. Is there anything specific you wish the reviewer to assist with. Do you have any concerns with this PR, why?