Initializes support for receiving Instagram WebHooks. Set the 'MS_WebHookReceiverSecret_Instagram
' application setting to the application secrets, optionally using IDs to differentiate between multiple WebHooks, for example 'secret0, id1=secret1, id2=secret2
'. The corresponding WebHook URI is of the form 'https://<host>/api/webhooks/incoming/instagram/{id}
'. For details about Instagram WebHooks, see https://www.instagram.com/developer/subscriptions/
.