Returns a Promise object or the 'this' object.
The required user is a string that identifies the user. The required password is a string that defines the password.
Options is a struct that can have the following items, all of which are optional.
Page is a string that defines the page to jump to or a function to call on success.
Promise determines the return value of this function. If promise has the value 'true' (the default), a Promise object is returned. If promise has the value 'false', the ‘this’ object is returned instead.
Success-function is a function called after the operation has successfully completed.
Error-function is a function called if an error occurs.