WhatsApp API Event Marketing Integration

I need the WhatsApp Business API wired into my existing marketing workflow so I can broadcast timely event announcements to my contact list. The goal is a seamless, permission-based flow: I draft an event update, hit send from my dashboard, and every opted-in subscriber receives it on WhatsApp within seconds.

Scope
• Acquire and activate the official WhatsApp Business API for my phone number (or link to my current Facebook Business account if that is faster).
• Build a reliable integration layer—webhook, middleware, or direct API calls—so future event messages can be triggered automatically or sent on-demand.
• Make the solution platform-agnostic. I have not locked in HubSpot, Mailchimp, or SendinBlue, so advise on the smoothest path or connect to a simple custom dashboard if that’s more efficient.
• Set up basic opt-in/opt-out handling to stay compliant with WhatsApp’s marketing policies.
• Provide a brief hand-off document (or short Loom video) covering how to push a new event announcement, view delivery reports, and update templates.

Acceptance criteria
1. A live test shows an event announcement arriving on at least two verified WhatsApp numbers.
2. Delivery status (sent/delivered/read) is visible from the chosen interface.
3. Opt-out reply “STOP” removes the contact automatically.

Tech preference is open—Node, Python, PHP, or a no-code bridge—so long as it is maintainable and can scale to a few thousand contacts per send.