[NDR-294] Refactor search fhir E2E tests to be more robust

[megan-bower4]

Description

NDR-294
Refactoring the fhir search E2E tests so that they identify the created resource, rather than all that relate to the given NHS number. This makes them more robust if there is ever left over data in the database.

Context

The search tests were giving unreliable results when run multiple times with other data in the db.

Checklist

• I have followed the code style of the project.
• I have added tests to cover my changes.
• I have updated the documentation accordingly.
• I have considered the cross-team impact when creating this PR and where possible written tests to validate for all affected.
• I have built a sandbox with code from this PR and ensured the unit tests and end-to-end tests have run successfully.
  https://github.com/NHSDigital/national-document-repository/actions/runs/19533351116 Run the E2E tests from this branch against ndr-dev
• A member of all teams has approved this PR if there is a major code change. (If this is a minor change and you are confident this is not necessary then you may accept the standard approval process of 2 approvals from any teams.)

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[github-actions]

Code security issues found

View full details here.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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