How Vehicle Body Groups and Form Serial Numbers Work

Source: `vehicle_body_groups_controller.rb`, `vehicle_form_serial_numbers_controller.rb`

• System-default body types are marked with no_delete and cannot be destroyed, even by administrators
• Body types that are in use by ANY company's vehicles across the entire system cannot be destroyed; they are globally protected
• Body group updates support creating and destroying entries in a single batch operation; body group codes are automatically uppercased on save
• Vehicle form serial numbers auto-use the company's next available form number; the date_printed field defaults to today's date
• Duplicate form serial numbers are checked by the combination of form_code + vehicle_id; the same form code can exist on different vehicles but not twice on the same vehicle

Support scenarios

• "I can't delete this body type" → Body types marked as system defaults (no_delete) can never be deleted. Additionally, any body type in use by any company's vehicles anywhere in the system is protected from deletion.
• "The body group code I entered was changed to uppercase" → Body group codes are automatically uppercased on save. This is normal behaviour to ensure consistency.
• "I got a duplicate form serial number error" → Duplicates are checked by form_code + vehicle_id combination. The same form code already exists on this vehicle. Use a different form code or check the existing form entry.
• "The form serial number wasn't what I expected" → Form serial numbers auto-assign from the company's next available number. If numbers appear to skip, a previous form may have been created and then deleted or the counter was advanced by another user.