Task: Create new member in Mailchimp when a request is made to a webhook URL

n8n workflow JSON:
{"nodes":[{"name":"Webhook","type":"n8n-nodes-base.webhook","position":[830,330],"webhookId":"710978c5-f61d-4622-be46-69251ecd3812","parameters":{"path":"710978c5-f61d-4622-be46-69251ecd3812","options":{},"httpMethod":"POST"},"notesInFlow":true,"typeVersion":1},{"name":"Mailchimp","type":"n8n-nodes-base.mailchimp","position":[1166,328],"parameters":{"list":"c478892a5e","email":"={{$node[\"Webhook\"].json[\"body\"][\"email\"]}}","status":"subscribed","options":{},"mergeFieldsUi":{"mergeFieldsValues":[{"name":"FNAME","value":"={{$node[\"Webhook\"].json[\"body\"][\"firstname\"]}}"}]}},"credentials":{"mailchimpApi":"Mailchimp Credentials"},"typeVersion":1}],"connections":{"Webhook":{"main":[[{"node":"Mailchimp","type":"main","index":0}]]}}}