Added validation checks when reviewing personal information

[dcyoung-dev]

Context

We want to check that the Immigration Status form is valid before allowing the Candidate to mark the Personal Details section as complete. Previously Candidates could mark this section as complete without selecting their Immigration Status.

Changes proposed in this pull request

• Added a validation check for the ImmigratioStatusForm for non-UK Canaidates when marking the Personal Details section as complete

Guidance to review

Before this PR

• With a new Canadidate, edit the "Personal information" section
• Add a first name, last name and dob
• select a non UK nationality
• On the immigration status page, navigate back to the "Your details" page
• Click on "Change" in the "Personal information" section
• Select "complete" and submit
• You will see the section has been completed but there will be no "Visa or immigration status" information

After this PR

• Following the same steps, when you mark the section as "Complete", the section will not complete.
• The Candidate will be shown the Review page without error - this will be fixed next as there are no validation errors on the page for any other form within this section.

Things to check

• If the code removes any existing feature flags, a data migration has also been added to delete the entry from the database
• This code does not rely on migrations in the same Pull Request
• If this code includes a migration adding or changing columns, it also backfills existing records for consistency
• If this code adds a column to the DB, decide whether it needs to be in analytics yml file or analytics blocklist, if included inform data insights team of the changes
• If this code adds a column that may include PII, the sanitise.sql script and 0025-protecting-personal-data-in-production-dump.md ADR have been updated
• API release notes have been updated if necessary
• If it adds a significant user-facing change, is it documented in the CHANGELOG?
• Attach the PR to the Trello card

[dcyoung-dev]

Trello: https://trello.com/c/2eH1p6bZ