expires_in token is sometimes a string in JSON response

[nadeemabdulhamid]

I suggest modifying this line:

webapi/webapi/private/oauth2.rkt

Line 281 in c1a172e

[new-expires-in (hash-ref json 'expires_in +inf.0)])

to:

         [new-expires-in/raw (hash-ref json 'expires_in +inf.0)]
         [new-expires-in (if (string? new-expires-in/raw)
                             (string->number new-expires-in/raw)
                             new-expires-in/raw)]

I was using this library with Microsoft OAUTH authentication and it looks like the expires_in field in the json response is being given back as a string by the server, so this tweak would apply string->number if a server does that.