Split FlowDelegate into DeviceFlowDelegate and InstalledFlowDelegate.

Each flow invokes a non-overlapping set of methods. There doesn't appear
to be any benefit in having both flows use a common trait. The benefit
of splitting the traits is that it makes it clear which methods need to
be updated for each flow type where previously comments were required to
communicate that information.

src/device.rs

@@ -1,4 +1,6 @@
-use crate::authenticator_delegate::{DefaultFlowDelegate, FlowDelegate, PollInformation, Retry};
+use crate::authenticator_delegate::{
+    DefaultDeviceFlowDelegate, DeviceFlowDelegate, PollInformation, Retry,
+};
 use crate::error::{Error, JsonErrorOr, PollError};
 use crate::types::{ApplicationSecret, Token};
 
@@ -24,7 +26,7 @@ pub const GOOGLE_GRANT_TYPE: &str = "http://oauth.net/grant_type/device/1.0";
 pub struct DeviceFlow {
     pub(crate) app_secret: ApplicationSecret,
     pub(crate) device_code_url: Cow<'static, str>,
-    pub(crate) flow_delegate: Box<dyn FlowDelegate>,
+    pub(crate) flow_delegate: Box<dyn DeviceFlowDelegate>,
     pub(crate) wait_duration: Duration,
     pub(crate) grant_type: Cow<'static, str>,
 }
@@ -36,7 +38,7 @@ impl DeviceFlow {
         DeviceFlow {
             app_secret,
             device_code_url: GOOGLE_DEVICE_CODE_URL.into(),
-            flow_delegate: Box::new(DefaultFlowDelegate),
+            flow_delegate: Box::new(DefaultDeviceFlowDelegate),
             wait_duration: Duration::from_secs(120),
             grant_type: GOOGLE_GRANT_TYPE.into(),
         }
@@ -93,7 +95,7 @@ impl DeviceFlow {
                 device_code,
                 grant_type,
                 pollinf.expires_at,
-                &*self.flow_delegate as &dyn FlowDelegate,
+                &*self.flow_delegate as &dyn DeviceFlowDelegate,
             )
             .await
             {
@@ -203,7 +205,7 @@ impl DeviceFlow {
         device_code: &str,
         grant_type: &str,
         expires_at: DateTime<Utc>,
-        flow_delegate: &dyn FlowDelegate,
+        flow_delegate: &dyn DeviceFlowDelegate,
     ) -> Result<Option<Token>, PollError>
     where
         C: hyper::client::connect::Connect + 'static,
@@ -278,7 +280,7 @@ mod tests {
     async fn test_device_end2end() {
         #[derive(Clone)]
         struct FD;
-        impl FlowDelegate for FD {
+        impl DeviceFlowDelegate for FD {
             fn present_user_code(&self, pi: &PollInformation) {
                 assert_eq!("https://example.com/verify", pi.verification_url);
             }