* add several methods to the sales log to allow subsequent work to be human readable
* add a validation to prevent an inconsistent combination of values and tests for this validation
* handle derivation of values around buyers living in the property
- derive values where appropriate
- clear these values when the derived state no longer holds
- update the routing for pages holding questions about whether particular buyers will live in the property to reflect when they are derived
- test the deriving and associated clearing of values
- update tests on page routing and sales log factory
* update a page routing condition for human readability using an existing method and update test to reflect this change
* show related method in diff
* minor amendments after tech review
* simplify reset_derived_questions after tech review
* refactor on deriving and clearing invalid derived values on sales log
* correct linter complaints
* remove comment
* add validation to one more field with a new error message as it is in fact possible to tirgger the validation in the setup section
* replace range validation with multiple to account for single-ended ranges
* add test for question with min but no max
* add min and max to household count question and remove bespoke validation. Remove code allowing max and no min given this situation does not seem to exist int eh form
* amend minor typo, add back a soft validation that had mysteriously gone missing
* Add old_persons_shared_ownership_value_check to sales table
* Move hard validation method to soft validation
* Add old persons shared ownership value check page and question
* Add pages to the household characteristics
* Add soft validation after ownership type
* update a test
* make old_persons_shared_ownership_value_check optional because it's in the setup section
* typo
* Add min and max for age 1 validation
* Add retirement value check column to the sales table
* Add retirement value check question and page
* Add retirement value check pages to household characteristics
* Reuse soft validations for retirement in sales
* Update person_indexes
* Add old_persons_shared_ownership validation
* Display the retirement value check in correct places depending on the joinpur value
* Update page IDs
* It's always joint purchase if age 2 is displayed
* lint
* lint
* Add min and max to age2 + questions
* validate that under 16s are economic children
* Update factory
* Update test
* Update ecstat, relationship and age validation