Playground doesn't ask for separate credentials. Instead, it allows login via popular identity providers so that users don't need to remember another set of credentials. Users can signup/login anytime with any of the supported providers, and they should be up & dashing.
Login matches the user’s email address explicitly within the Playground. It allows you to log in even if you are using different identity providers the second time, making the whole process simple.
- Signup/Login methods match with an email address.
- Any provider can be used to login into account until & unless the email address is the same.
- Users will not have access to this app if, for some reason, they don't own the original email address with which they logged in.