Initiate an Upload with the App Engine

Does anyone know if it is possible to initiate an upload with the app-engine? For example we want to run a slash command, open up a modal, and then select file/image(s) to upload from the modal. Wasn’t sure what was exposed to the app-engine that would allow for this or if anyone has done this before. Thank you in advance!

I may have answered my own question with this: IUploadCreator | Rocket.Chat Apps TypeScript Definition. But if anyone has any other comment to share on this it would be appreciated. Thank you!