schema creation and validation functions without panicing

[zzzming]

Fixes #793

#793

Motivation

This is an API improvement to avoid panic for any user recoverable error when a schema is created.

User should handle any codec error if the NewAvroSchema returns an error reference, although a user can still write a panic recovery procedure but that is not a standard way to do error handling.

Modifications

Introduce three additional functions to create JSON, Proto, and Avro schema with error returned without panic. The existing functions are kept for backward compatibility.

Verifying this change

• Make sure that the change passes the CI checks.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (yes)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)

New APIs are introduced to return any errors when schema codec creation fails. The legacy API are kept.

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / GoDocs / not documented)
• If a feature is not applicable for documentation, explain why?
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[eolivelli]

Lgtm

[michaeljmarshall]

LGTM