POST /token HTTP/1.1
Content-Length: 112
user-agent: ericnorris/gcp-auth-contrib unit test
Host: oauth2.googleapis.com
Accept: application/json
Content-Type: application/x-www-form-urlencoded

grant_type=a-grant-type&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcloud-platform&assertion-field=assertion