PartitionedFileSetArguments.addInputPartition should also specifying a PartitionKey.
Currently, it requires that the user pass in a Partition object.
If a user knows which PartitionKey(s) they want to process, the current API requires that the user instantiate the PartitionedFileSet, and fetch the Partition objects for each of the keys. This step can be bypassed if the API allows the user to just specify the PartitionKey(s).
This will also resolve the following TODO: