Use email instead of username for USER_PASS authentication strategy

[khrj]

When using the USER_PASS authentication strategy via the player API, spotify fails to authenticate if the username is an email address. For users that originally signed up using Google and later added an email, the username is a generated string of characters like odnl14ixxxxxxxxxxxxxxxxxxxx.

However, somehow, the binary downloaded from releases seems to be able to work when the username supplied is an email.

How do I authenticate using an email address using the player API?