[API Callout] Named Credential + External Credential

Use Case

We're using SendGrid for Email Marketing, and we have created a webservice and exposed MQL lead generation service via Site page as incoming webhook event handler.

In the webservice, once we detect a click event on links, we capture the email info, and callout get contacts by emails API to enrich lead.

In my use case, I try to use named credentials for auth part, so I can easily manage the API_Key in Salesforce, and reuse the auth logic.

System Config

Named Credentials Setup

Profile Setup (Guest User's Profile View)