Allow for html injection of content

[ifielder]

Goals

1. Easy migration of existing html templates from Mailchimp and sendgrid
2. Add dynamic content like existing blog posts and newsletter markup
3. Allow a collection of templates where the content of the email is dynamic, but the style is consistent.

Background

injection of HTML in email templates is a useful feature because it allows developers to create reusable templates that can be customized for each individual recipient. This is particularly useful for marketing campaigns or newsletters where each recipient may need to see slightly different content, but the overall design and structure of the email remains the same. By using placeholders in the email template, developers can easily inject dynamic content into the email at runtime, making the process of creating personalized emails much easier.

Prior art for this feature can be found in email service providers like SendGrid, which already provide this functionality for their users. SendGrid's email templates allow users to define a template file with placeholders for dynamic content, and then pass in data to fill in those placeholders at runtime. This approach has been widely adopted by email marketers and developers as a best practice for creating engaging and personalized email campaigns.

Proposal

I suggest that this feature could work in a similar way to how templates work in the SendGrid email service. Specifically, users could define template files with placeholders for dynamic content, and then pass in data to fill in those placeholders at runtime. This would enable developers to create reusable email templates with dynamic content that could be customized for each individual recipient.