Reset specific file upload page state when a failure occurs

[alexluckett]

Proposed change

Jira ticket: https://eaflood.atlassian.net/browse/DF-719

Type of change

When a file upload question becomes invalid, only invalidate the one page that's affected rather than all pages. We do this by creating a new getStateKeys function at page controller level, which can declare supplementary state values to clear in addition to the core component state.

• Bug fix
• New feature
• Breaking change
• Misc. (documentation, build updates, etc)

Checklist

• You have executed this code locally and it performs as expected.
• You have added tests to verify your code works.
• You have added code comments and JSDoc, where appropriate.
• There is no commented-out code.
• You have added developer docs in README.md and docs/* (where appropriate, e.g. new features).
• The tests are passing (npm run test).
• The linting checks are passing (npm run lint).
• The code has been formatted (npm run format).

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
92.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud