Fix (forms): update schema for "redirect business mail" api

[sajclarke]

Description

This PR updates the post-office redirection form for businesses to align with the Figma design specifications. It includes schema restructuring to improve form organization and enhances validation to properly reject empty strings for required fields.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Changes Made

• Restructure business form schema to prioritize business name field at top level
• Rename "oldBusinessAddress" to "currentAddress" for clarity
• Update form field organization and grouping
• Update field labels for consistency (e.g., "Address Line 1" → "Address line 1")
• Add postcode field with Barbados postal code validation (BB#####)
• Remove personal applicant details (title, firstName, lastName, dateOfBirth, etc.) from primary scope
• Improve string validation to reject empty strings for required fields
• Refactor schema-builder service to properly handle empty string validation
• Add explicit validation for required fields that enforces minimum length of 1 character
• Consolidate validation logic to consistently treat required vs optional string fields

Files Changed

• schemas/post-office-redirection-business.json - Form schema restructuring (98 insertions, 103 deletions)
• src/validation/schema-builder.service.ts - Enhanced string validation logic (35 changes: improved empty string handling and required field validation)

Notes

The validation improvements ensure that required string fields cannot be submitted with only whitespace or empty values, preventing invalid data from reaching the backend. The schema restructure makes the form more intuitive by presenting the business name first and reorganizing address sections logically.

Testing

• Form validation tested with empty string inputs
• Verify required fields reject whitespace-only values
• Test optional fields accept empty strings
• Verify form renders correctly with new schema structure
• Test postcode validation (BB##### format)
• Validate all parish selection works correctly
• Check form submission with complete and partial data
• Test responsive design across device sizes

Related Github Issue(s)/Trello Ticket(s)

Checklist

• Code follows project style guidelines
• Self-review completed
• Tests added/updated for validation logic
• Documentation updated
• Validation rules tested with edge cases

[amazon-inspector-n-virginia]

⏳ I'm reviewing this pull request for security vulnerabilities and code quality issues. I'll provide an update when I'm done

[amazon-inspector-n-virginia]

✅ I finished the code review, and didn't find any security or code quality issues.