You can login to some platforms for example younow.com (only) with the login data
of other platforms like Twitter/Facebook/Goolge+/Instagram.
I have read anywhere about tokens are used for it. But I don't know more.
So I have some questions:
If users log in to my platform with Twitter etc:
Have I still to create a database to save user login and further data?
Or are all user and other data saved at Twitter etc and I don't need
my own database?
If all data saved at Twitter etc: Isn't that dangerous for me
because I'm dependent on Twitter etc to get user data I need
(how many likes/coins the user has for example)?
If I have to save all the data too in my database : Why should I use other login services?
How do I link a token from Twitter etc to the user data in my database?
I think on every login with Twitter another token is generated.
How can I link a token to the right user in my database (if I also have to save user data)?
Or how do I know it's the same user if there are always new tokens for the same user?
How can the login with other platforms like Twitter be implemented?
Is it complicated? Is there code anywhere?
Have I to enter a contract with Twitter etc to use
there login for my login?
I don't know enough for further questions.
What else is important to know?