Create a webhook

Available event types:<br/>- subscriber.subscriber_activate<br/>- subscriber.subscriber_unsubscribe<br/>- subscriber.subscriber_bounce<br/>- subscriber.subscriber_complain<br/>- subscriber.form_subscribe, required parameter form_id [Integer]<br/>- subscriber.course_subscribe, required parameter sequence_id [Integer]<br/>- subscriber.course_complete, required parameter sequence_id [Integer]<br/>- subscriber.link_click, required parameter initiator_value [String] as a link URL<br/>- subscriber.product_purchase, required parameter product_id [Integer]<br/>- subscriber.tag_add, required parameter tag_id [Integer]<br/>- subscriber.tag_remove, required parameter tag_id [Integer]<br/>- purchase.purchase_create<br/>- custom_field.field_created<br/>- custom_field.field_deleted<br/>- custom_field.field_value_updated, required parameter custom_field_id [Integer]