refs https://github.com/TryGhost/Toolbox/issues/292
- When the handler recognizes a Zapier client it should send an email using Zapier-specific template with instructions more suitable for Zap failure
refs https://github.com/TryGhost/Toolbox/issues/292
- The html/text emails is a desired system that's used in Ghost core and should be reused with version mismatch notification emails too.
- Currently there's only one template defined "generic-mismatch" and the original file for it can be found under /templates/generic-mismatch.html
- If we need to distinguish user agents we can addd more templates to the `/templates/` folder
