Twilio SendGrid Email Integration

We are building a multi-channel notification platform on a Python/Django B2B SaaS. Phase 0 is tightly scoped: one internal business trigger, one channel — transactional email via Twilio SendGrid — plugged into our existing outbox infrastructure.
This is explicitly a Twilio ecosystem engagement. The ChannelAdapter interface you build now must accommodate Twilio Messages API (WhatsApp/SMS) in Phase 1 and Twilio Conversations API + Conversational Relay with OpenAI GPT-4o in Phase 2 — without touching the core. Twilio-specific knowledge matters here: understanding how SendGrid sits within the Twilio product family, how dynamic_template_data maps to Handlebars variables inside Twilio SendGrid Dynamic Templates, and how the SendGrid Event Webhook signature validation works (X-Twilio-Email-Event-Webhook-Signature) is part of the job.