The `meta` field validation is too loose

[NevilleS]

From fideslang created by ThomasLaPiana: IABTechLab#127

Bug Description

The meta field now allows bytes, which immediately blow up when serialized to JSON

Expected behavior

The meta field should automatically convert all bytes to strings so that it can be JSON serialized and sent via API

Additional context

This bug was found in fidesplus when the system scanner tests blew up