use region to look up hesa code if post code is not helpful

[elceebee]

Context

Changes proposed in this pull request

Guidance to review

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
• [ ] 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
• [ ] This code adds a column or table to the database
  • [ ] This code does not rely on migrations in the same Pull Request
  • [ ] decide whether it needs to be in analytics yml file or analytics blocklist
  • [ ] data insights team has been informed of the change and have updated the pipeline
  • [ ] the sanitise.sql script and 0025-protecting-personal-data-in-production-dump.md ADR have been updated
  • [ ] does the code safely backfill existing records for consistency

[elceebee]

Bug: Postcodes that span multiple countries do not return a domicile code