Provide guidance on PATCHing arrays

[a-akimov]

must-update-parts-of-a-resource-via-patch-to-a-resource-uri

Consider also mentioning how array-type properties are PATCH'ed. I assume the new array sent in a request fully replaces the old array rather than appends to it. Some APIs I've worked with provide an option whether to replace or append arrays. This can be useful if the array contains complex objects.