Added cancellation_path in dependency injection configuration
Added CancellationRequest and CancellationParameterResolver
Added transport layer to handle cancellation request
Added transport definition + services, updated configuration
Added CancellationParameterResolverTest
Added CancellationRequest unit test
Added unit test for transport layer
Fixed some typo
Refactored transport configuration
Fixed breaking CurlTransport unit test
Merge pull request #1 from fabienpomerol/feat-cancellation

Added  Subscription Cancellation
Removed ETAT_PBX parameter to verify signature on IPN call