Task: Send a message on Mattermost when an order is created in WooCommerce

n8n workflow JSON:
{"id":"188","name":"Send a message on Mattermost when an order is created in WooCommerce","nodes":[{"name":"WooCommerce Trigger","type":"n8n-nodes-base.wooCommerceTrigger","position":[550,260],"webhookId":"84960a7c-cb69-4dfb-a5ed-aac12e0efbf8","parameters":{"event":"order.created"},"credentials":{"wooCommerceApi":"woocommerce"},"typeVersion":1},{"name":"Mattermost","type":"n8n-nodes-base.mattermost","position":[750,260],"parameters":{"message":"={{$node[\"WooCommerce Trigger\"].json[\"billing\"][\"first_name\"]}} bought {{$node[\"WooCommerce Trigger\"].json[\"line_items\"][0][\"name\"]}}!","channelId":"pj1p95ebei8g3ro5p84kxxuuio","attachments":[],"otherOptions":{}},"credentials":{"mattermostApi":"Mattermost Credentials"},"typeVersion":1}],"active":false,"settings":{},"connections":{"WooCommerce Trigger":{"main":[[{"node":"Mattermost","type":"main","index":0}]]}}}