Change log description
Extract the Event type schema from the avro union schema.

Purpose of the change
Fixes #59

What the code does
With avro schema definitions, an avro file can include a union schema of multiple types which allows referencing same type in multiple places in the schema.
If a union type is sent to service, with type as one of the types in the union, we extract the type from the union
and normalize the schema for the type using the nested structure retrieved from the Schema object.

How to verify it
TBD