Problem/Motivation
I'm using migrate to create/update entities based on data that's pushed from an external system. I want to support partially updating existing entities: updating only the fields that are present in the array, while skipping the ones that are missing. Properties should still be able to unset by setting the key to a null value.
As far as I know, this is currently not possible. No distinction is made between empty properties and missing properties.
Steps to reproduce
Migrate data with only part of the source properties available. All properties that aren't passed will be emptied on the destination entity.
Proposed resolution
Provide a configuration option on the content entity destination plugin, skip_missing_properties, that makes sure that missing source properties are not emptied in the destination entity.