refactor(DeviceFlow): Make DeviceFlow work with Futures

examples/test-device/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "test-device"
+version = "0.1.0"
+authors = ["Lewin Bormann <lewin@lewin-bormann.info>"]
+edition = "2018"
+
+[dependencies]
+yup-oauth2 = { path = "../../" }
+hyper = "0.12"
+hyper-tls = "0.3"
+futures = "0.1"
+tokio = "0.1"

examples/test-device/src/main.rs

@@ -0,0 +1,26 @@
+use futures::prelude::*;
+use yup_oauth2;
+
+use hyper::client::Client;
+use hyper_tls::HttpsConnector;
+use std::path;
+use tokio;
+
+fn main() {
+    let creds = yup_oauth2::read_application_secret(path::Path::new("clientsecret.json"))
+        .expect("clientsecret");
+    let https = HttpsConnector::new(1).expect("tls");
+    let client = Client::builder().build::<_, hyper::Body>(https);
+
+    let scopes = &["https://www.googleapis.com/auth/youtube.readonly".to_string()];
+
+    let ad = yup_oauth2::DefaultAuthenticatorDelegate;
+    let mut df = yup_oauth2::DeviceFlow::new::<String>(client, creds, ad, None);
+    let mut rt = tokio::runtime::Runtime::new().unwrap();
+
+    let fut = df
+        .retrieve_device_token(scopes.to_vec())
+        .and_then(|tok| Ok(println!("{:?}", tok)));
+
+    rt.block_on(fut).unwrap()
+}