Add Insecure Client for Convenience

[tstirrat15]

Fixes #89

Description

One thing that most users of our library run into is that you can't use client credentials in a non-TLS context with the way that the Python gRPC lib is designed. This was likely intentional; network sniffing can turn into credential exposure in a production environment. However, it's frustrating and inconvenient when all you want to do is try out the lib using docker-compose.

This provides an InsecureClient that implements a workaround for those contexts.

Changes

• Add grpc-interceptor as a dep for setting up the new interceptor
• Reorganize some code to make things more reusable
• Add an InsecureClient to allow for the use case

Testing

Review. See that tests pass and that you can set up a connection with the InsecureClient.