Provides an IWebHookReceiver implementation which supports WebHooks generated by MailChimp. A sample WebHook URI is 'https://<host>/api/webhooks/incoming/mailchimp/{id}?code=83699ec7c1d794c0c780e49a5c72972590571fd8'. For security reasons the WebHook URI must be an https URI and contain a 'code' query parameter with the same value as configured in the 'MS_WebHookReceiverSecret_MailChimp' application setting. The 'code' parameter must be between 32 and 128 characters long. For details about MailChimp WebHooks, see https://apidocs.mailchimp.com/webhooks/.