Provides an IWebHookReceiver implementation which supports WebHooks generated by Pusher. The 'MS_WebHookReceiverSecret_Pusher
' application setting contains a semicolon separated list of values of the form 'appKey_appSecret
' containing one or more application key/secret pairs defined in Pusher. An example with two key/secret pairs is '47e5a8cd8f6bb492252a_42fef23870926753d345; ba3af8f38f3be37d476a_9eb6d047bb5465a43cb2
'. The corresponding WebHook URI is of the form 'https://<host>/api/webhooks/incoming/pusher/{id}
'. For details about Pusher WebHooks, see https://pusher.com/docs/webhooks
.