Email client, application startup logic and tests

tests/api/health_check.rs

@@ -0,0 +1,16 @@
+use crate::helpers::TestApp;
+
+#[tokio::test]
+async fn health_check_works() {
+    let app = TestApp::spawn().await;
+    let client = reqwest::Client::new();
+
+    let response = client
+        .get(format!("http://{}/health_check", app.address))
+        .send()
+        .await
+        .unwrap();
+
+    assert!(response.status().is_success());
+    assert_eq!(Some(0), response.content_length());
+}