JWT payload is not decoded properly

[abhishek97]

I was just trying to implement a jwt token auth with refresh token for my app, however, i was getting this error when ember-simple-auth-token tries to decode the jwt received from the server

Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.

I looked into the issue for a bit, tracked it down to this line: https://github.com/jpadilla/ember-simple-auth-token/blob/master/addon/authenticators/jwt.js#L284

The thing is we try to do a base64 decode, however as specified in the JWT rfc7519(https://tools.ietf.org/html/rfc7519), the payload is base64url encoded, so window.atob will fail to decode it.

[abhishek97]

I seemed to have fixed this, I have also submitted the PR for the same. If someone can look into it please