DataFile should not accept an empty roles keyword argument

[mcduffie]

The DataFile STAC catalog wrapper class should not allow the role keyword argument to be an empty list:
https://github.com/unity-sds/unity-monorepo/blob/main/libs/unity-py/unity_sds_client/resources/data_file.py

Since this is an MDPS specific class, it should throw an exception if one of the role types valid for U-DS data ingestion is not specified. This can help prevent users from failing to have data ingested when using the interface.