Fixed restoration of state from save and exit if partial page

[jbarnsley10]

Proposed change

Fixed restoration of state from save and exit if partial page.
When we save the payload of a Declaration component (before it goes into state for a partial page 'save-and-exit' operation), it hasn't got the same structure as when in state.
The payload structured will be ['true', 'unchecked'] if checked, and ['unchecked'] if unchecked.
This fix caters for that scenario to set the Declaration checkbox to the correct value.

Jira ticket: DF-607

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
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud