I have a web app in php mysql, I want to use one google drive account for my app. Can I use my app's accounts instead of google users for privilages. I read in SDK I can use service account to login without promting user, but I don't know how to share or give permissions files for custom users. In api reference I found this: "The user is not necessarily yet a Google user (e.g. if a file or folder is shared with an email address that does not yet have an associated Google account). Example: 1111459233037698895607". How a custom user in my app should get a token for own privilages.