Custom IDP provider wrong check for login method

[pekura]

A custom IDP provider must fulfill certain condition, for example it must implement the 'login' function. The check for existence of this function is wrong though. If you specify a custom IDP like this:

class CustomIDPProvider {
      login() {
        // do stuff
      }
}

you get following error: "Error: login function does not exist in custom IDP Provider custom".

You need to add 'login' property to the CustomIDPProvider addtitionally, like this:

CustomIDPProvider.login = function() {};

This should not be necessary. The login function of the class is used effectively.