SetOptions
interface
An options object that configures the behavior of set() calls in DocumentReference, WriteBatch and Transaction.
These calls can be configured to perform granular merges instead of overwriting the target documents in their entirety
by providing a SetOptions with merge: true.
Using both merge and mergeFields together will throw an error.
Properties
merge
</>Changes the behavior of a set() call to only replace the values specified in its data argument.
Fields omitted from the set() call remain untouched.
merge: undefined | false | true;
