avro

AVRO-3433: Rust: The canonical form should preserve schema references (#1580)

* AVRO-3433: Rust: The canonical form should preserve schema references

Do not resolve Schema::Ref when printing as JSON.
The Java SDK complains that a type is redefined if it is not a Ref the
second time

Signed-off-by: Martin Tzvetanov Grigorov <mgrigorov@apache.org>

* AVRO-3433: Use Name as a key for parsed/resolving/input schemata

This is needed to have the fullname (namespace + '.' + name) for lookups

Signed-off-by: Martin Tzvetanov Grigorov <mgrigorov@apache.org>

* AVRO-3433: Name::new("...") should parse the optional namespace

This is a breaking change but a bug fix to properly implement the Avro specification

Signed-off-by: Martin Tzvetanov Grigorov <mgrigorov@apache.org>