Add `/devices/knowndevice` endpoint

Added a new endpoint which the currently beta client for at least
Android v2022.10.1 seems to be calling, and crashes with the response we
currently provide

Fixes #2890
Fixes #2891
Fixes #2892

src/api/core/accounts.rs

@@ -36,6 +36,7 @@ pub fn routes() -> Vec<rocket::Route> {
         verify_password,
         api_key,
         rotate_api_key,
+        get_known_device,
     ]
 }
 
@@ -739,3 +740,16 @@ async fn api_key(data: JsonUpcase<SecretVerificationRequest>, headers: Headers,
 async fn rotate_api_key(data: JsonUpcase<SecretVerificationRequest>, headers: Headers, conn: DbConn) -> JsonResult {
     _api_key(data, true, headers, conn).await
 }
+
+#[get("/devices/knowndevice/<email>/<uuid>")]
+async fn get_known_device(email: String, uuid: String, mut conn: DbConn) -> String {
+    // This endpoint doesn't have auth header
+    if let Some(user) = User::find_by_mail(&email, &mut conn).await {
+        match Device::find_by_uuid_and_user(&uuid, &user.uuid, &mut conn).await {
+            Some(_) => String::from("true"),
+            _ => String::from("false"),
+        }
+    } else {
+        String::from("false")
+    }
+}