Partial updates/adding new fields

[darri89]

According to the Algolia documentation, partial update of data should be possible, where multiple data sources each have a part of the data which should be indexed in to Algolia records. (See: https://www.algolia.com/doc/guides/indexing/updates-strategy/#partial-updates)

This does not seem to be possible with the current Scala DSL. All of the use cases I've seen for the partial update commands just seem to be modifying a single value that exists, not adding a new field to the record.

We really need this functionality for the project we are working on.