Im looking to be able to add an pdf invoice hosted by stripe to an email sent via Parse.Cloud.sendEmail. is this possible ?
It should be possible using the Parse Server API Mail Adapter. You should be able to pass a custom payload (like the file path you want to send), and then in the ApiPayloadConverter use that property to load the file and serve the file in a format that is understood by the email service provide of your choice.
Note that none of the existing payload converters currently support that (Mailgun, AWS Simple Mail Service). If you use one of these provider you could open a PR to extend the converter. If you are using another provider, you’d have to create a new converter, which should be easy if you look at the existing converters.