n8n WhatsApp API Integration

I want to build a fully-functional WhatsApp Business API workflow inside n8n that can both send and receive messages. The core flow should:

• Connect n8n to the official WhatsApp API and expose a webhook so every incoming message—text, image or video—arrives in the workflow in real time.
• Read outgoing content from two sources:
– a Google Sheets doc that holds free-form message text (columns: phone, message, status, optional media URL)
– predefined WhatsApp template messages stored locally or in MongoDB.
• Handle media uploads when the sheet includes an image or video link, then dispatch the file through the WhatsApp endpoint.
• Push delivery status and the full chat history back to both Google Sheets and MongoDB so I have an auditable log.

I already have WhatsApp Business credentials and n8n running; you just need to supply the n8n workflow files (JSON), any helper scripts, and a short README that explains environment variables, setup steps, and how to add new templates. Everything must be tested in Postman or a similar tool so I can plug in my tokens and run straight away.