fix/DF-717: Fixed ref-num being double-generated

[jbarnsley10]

Proposed change

Fix to prevent the ref num being generated afresh after form submission.
The ref num is now stored in confirmationState, and the confirmation page reads it from there, since the main state has already been cleared by the time the confirmation page is displayed (previously this was auto-generating another ref num).

Jira ticket: DF-717

Type of change

• 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
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud