spawn app for each integration test

also adds missing dep to flake

tests/common/mod.rs

@@ -0,0 +1,16 @@
+use std::net::TcpListener;
+
+pub fn spawn_app() -> String {
+    let listener = TcpListener::bind("127.0.0.1:0").expect("Failed to bind random port");
+    let _ = listener.set_nonblocking(true);
+    // We retrieve the port assigned to us by the OS
+    let port = listener.local_addr().unwrap().port();
+    let server = nuchat::run(
+        tokio::net::TcpListener::from_std(listener)
+            .expect("Failed to convert from_std to tokio listener"),
+    )
+    .expect("Failed to bind address");
+    tokio::spawn(server.into_future());
+    // We return the application address to the caller!
+    format!("http://127.0.0.1:{port}")
+}