Clickstream Event Publishing via Courier

[lucmahn88]

Background

As part of initiative of providing alternative network protocols in Clickstream SDK.

What does the PR do?

Milestone 3: Clickstream Event Publishing via Courier

• Add Courier's adapter type of EnvelopeMessage contract in Sample app
• Add URLRequest to replace base URL, path, queries, & headers in Courier config
• Update provideClientIdentifiers(..) API function
• Update CourierHandler to support HTTP polling fallback

Unit Test