WooCommerce Help Scout 3.9.3

* PLUGINS-997 - Fix various notice errors.
* PLUGINS-207 - Validation errors.
* PLUGINS-1241 - Add tab for ticket.
* PLUGINS-1192 - Add a filter to hide helpscout in customer order page.
* PLUGINS-381 - Cancel WooCommerce Subscriptions
* PLUGINS-379 - Refund WooCommerce Charges Inside Help Scout
* PLUGINS-1242 - Show conversation history on reply.
* PLUGINS-1293 - Code improvement.

* PLUGINS-1002 - Fix customer data not syncing on HelpScout mailbox.

* PLUGINS-1240 - Incorrect API credentials should display useful message