Store device_id in session

The device_id is needed by the client, but otherwise inaccessible (unless
provided to the server by the client).
This is analogous to how the user_id is currently stored for guests, but
will probably be more often used.  The device_id is needed to implement e2e
encryption.

src/lib.rs

@@ -114,7 +114,7 @@ where
             },
         )
         .map(move |response| {
-            let session = Session::new(response.access_token, response.user_id);
+            let session = Session::new(response.access_token, response.user_id, response.device_id);
             *data.session.borrow_mut() = Some(session.clone());
 
             session
@@ -142,7 +142,7 @@ where
             },
         )
         .map(move |response| {
-            let session = Session::new(response.access_token, response.user_id);
+            let session = Session::new(response.access_token, response.user_id, response.device_id);
             *data.session.borrow_mut() = Some(session.clone());
 
             session
@@ -179,7 +179,7 @@ where
             },
         )
         .map(move |response| {
-            let session = Session::new(response.access_token, response.user_id);
+            let session = Session::new(response.access_token, response.user_id, response.device_id);
             *data.session.borrow_mut() = Some(session.clone());
 
             session

src/session.rs

@@ -7,14 +7,17 @@ pub struct Session {
     access_token: String,
     /// The user the access token was issued for.
     user_id: UserId,
+    /// The ID of the client device
+    device_id: String,
 }
 
 impl Session {
     /// Create a new user session from an access token and a user ID.
-    pub fn new(access_token: String, user_id: UserId) -> Self {
+    pub fn new(access_token: String, user_id: UserId, device_id: String) -> Self {
         Session {
             access_token,
             user_id,
+            device_id,
         }
     }
 
@@ -27,4 +30,9 @@ impl Session {
     pub fn user_id(&self) -> &UserId {
         &self.user_id
     }
+
+    /// Get ID of the device the session belongs to.
+    pub fn device_id(&self) -> &str {
+        &self.device_id
+    }
 }