Hi there,
The requirements are quite clear and straightforward to implement so no questions really. API will consist of 2 components, authentication and file upload. You'll be able to manage authentication component through flask-admin, a clean, basic yet fully functional package.
I am planning to use python 3 branch. If you instead prefer python 2 branch just let me know please. Per your request I will install it on your servers via Teamviewer once it's ready for deployment, thanks.