Support for protobuf schemas

**Is your feature request related to a problem? Please describe.**
In a Microsoft environment, protobuf is generally preferred to Avro and JSON Schema. It would be nice to be able to use this client with protobuf schemas as well!

**Describe the solution you'd like**
Implement the existing interfaces using protobuf as has already been done for avro and json schema.

Start by locating the existing interfaces and the Avro and JSON Schema implementations referenced in the issue. Compare how those schema types are integrated, then determine the corresponding protobuf entry point and verification needed. Done means the client supports protobuf schemas through the same interfaces as the existing implementations.

Written by the indexing model from the issue text.