getChildSchemaSelection
  ✔️ should resolve items from oneOf elements
  ✔️ should return a single array-item as list
  ✔️ should return a single object-schema as list
  ✔️ should return an empty array if items schema is undefined
  ✔️ should return list of oneOf elements
getChildSchemaSelection additionalItems
  ✔️ should not return additionalItems if item-schema is object
  ✔️ should return additionalItem schema
  ✔️ should return additionalItem schema when items-list is exceeded
  ✔️ should return items-schema instead of additionalItems if item is defined