Enable User Cards Upload

[Christiane (Tina) Heiligers]

Users should be able to upload their own cards.
To be decided:

• Users have to create an account before uploading cards (Google, twitter) so that we can capture further details of each user to block them, to prevent/stop/catch them from uploading malicious or inappropriate content.
• No account required: all users can upload card images, these are stored in a temp bucket, reviewed and approved -> drawback: loads of further work for me!