feat: shared IONOS HTTP client with retry/backoff

tests/ionos_tests.rs

@@ -0,0 +1,25 @@
+use alpha_id::ionos::IonosClient;
+use std::io::Write;
+
+fn mock_server(body: &'static str) -> (String, std::thread::JoinHandle<()>) {
+    let server = tiny_http::Server::http("127.0.0.1:0").unwrap();
+    let url = format!("http://{}", server.server_addr());
+    let h = std::thread::spawn(move || {
+        if let Ok(req) = server.recv() {
+            let resp = tiny_http::Response::from_string(body);
+            req.respond(resp).ok();
+        }
+    });
+    (url, h)
+}
+
+#[test]
+fn posts_json_and_parses_response() {
+    let (url, h) = mock_server(r#"{"ok":true}"#);
+    let mut tf = tempfile::NamedTempFile::new().unwrap();
+    write!(tf, "test-token-123").unwrap();
+    let c = IonosClient::new(&url, tf.path().to_str().unwrap()).unwrap();
+    let v: serde_json::Value = c.post_json("/ping", &serde_json::json!({"x":1})).unwrap();
+    assert_eq!(v["ok"], true);
+    h.join().ok();
+}