How to upload data to the cloud through a third-party site?

Question

Data storage

Hello. I'm not an IT person myself, I work as a dentist, help me clarify one thing: (I apologize right away if I write all sorts of nonsense)
Let's say I want to make a site where you can upload x-rays of patients and do certain calculations (for example, measure the length of the roots in mm ).
As I understand it, all pictures should be stored on the server, i.e. I have to pay for data storage.
The question is - can you make sure that all these pictures are stored in the cloud storage of the person who uploaded them? Let's say there is a doctor, he has paid a tariff for 100 GB in Google Drive, and so that I do not have to store his pictures on the server of my site, they will be uploaded to his cloud through my site?
Is it possible to do so at all? Is this from the realm of fantasy?
Again, I don't understand this.)

Answer 1

It is possible, but very difficult. Cheaper and easier to pay for and use the cloud
The idea is bad, so it's better to put it out of your head

Answer 2

Yes, it is possible to do so. But usually this is not done))
You can do authorization through Google on the site and connect the disk there