feat: Add event subscription option to webhooks (#4540)

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

db/migrate/20220424081117_add_subscriptions_to_webhooks.rb

@@ -0,0 +1,12 @@
+class AddSubscriptionsToWebhooks < ActiveRecord::Migration[6.1]
+  def change
+    add_column :webhooks, :subscriptions, :jsonb, default: %w[
+      conversation_status_changed
+      conversation_updated
+      conversation_created
+      message_created
+      message_updated
+      webwidget_triggered
+    ]
+  end
+end