driver-core/src/main/com/mongodb/client/model/Updates.java
public static <TItem> Bson addEachToSet(final String fieldName, final List<TItem> values) {
        return new WithEachUpdate<TItem>(fieldName, values, "$addToSet");
    }
public static <TItem> Bson addEachToSet(final String fieldName, final List<TItem> values) {
        return new WithEachUpdate<TItem>(fieldName, values, "$addToSet");
    }
Creates an update that adds each of the given values to the array value of the field with the given name, unless the value is
already present, in which case it does nothing

@param fieldName the non-null field name
@param values    the values
@param <TItem>   the value type
@return the update
@mongodb.driver.manual reference/operator/update/addToSet/ $addToSet