PATCH 2xx should check each property individually

[robinmackaij]

For 2xx PATCH request, there are now 2 calls: one with all required and optional properties set and one with only required properties (which can result in a request with 0 modifications). Especially for PATCH, it is valuable to PATCH each property individually since for PATCH, the schema generally has only optional properties and those properties are often required for POST and PUT.