Replace customer field settings

Creates, updates, reorders and deletes customer custom field definitions, updates the optional-field visibility toggles and the birthday agenda switch in one call.

custom_fields is the complete list: an entry with id updates that field (values stored on customers are kept), an entry without id creates one (the id is returned), an existing field left out is deleted. Array position is the display order. When custom_fields is absent the definitions are left unchanged.

Omitted attributes are kept, never reset: an absent field_visibility key, an absent birthday_calendar_event, and an absent visible or reminder_days_before on an existing field all keep their stored value. New fields default to visible: true and no reminder.

Only the birthday and the internal notes can be hidden; fiscal, price-list and e-invoicing fields always show.

A hidden field creates no agenda events whatever its switch says; the switch stays stored and applies again once the field is shown. With field_visibility.birthday set to false no birthday events are created even when birthday_calendar_event is true. Events already in the agenda are never touched here.

Returns 422 parameter_invalid (with param pointing at the entry) for an unknown or repeated id, a repeated name (case-insensitive), a name outside 2–30 characters, an unknown type or more than 10 fields.