Project unit sales can now be reported for plot housing form

Changes to the API since 037.

Changed

In the "Create a project unit sale" endpoint, livingArea and numberOfRooms are no longer required when housingForm is 500 (Plot / Tomt). For all other housing forms both fields are still required on create.

This allows brokers to report sales of plot project units, which can then be included in Andelstatistiken (sale statistics).