Send missed appointment rescheduling emails with webhook and Gmail

Description

Quick Overview
This workflow receives missed-appointment events via a webhook, validates and filters them, then sends a single rescheduling email through Gmail and returns a JSON acknowledgement to the caller.

How it works
Receives a POST webhook request containing appointment and contact details.
Validates that event_id, contact.email, and appointment.id are present, then builds a rescheduling email message using the configured business name, booking URL, and subject.
Blocks processing when the appointment status is not missed or when transactional_contact_allowed is false.
Sends a plain-text rescheduling email to the contact via Gmail when the event is allowed.
Returns a JSON webhook response confirming acceptance and indicating whether the event was blocked.

Setup
Configure the webhook URL in your CRM/scheduling system to send missed-appointment events to this workflow’s webhook path.
Connect a Gmail credential and verify the sending mailbox used to deliver the rescheduling email.
Update the business name, booking URL, and email subject used in the outgoing message.