add http-json, rss, and media data source adapters

http-json: generic HTTP+JSON polling adapter, converts serde_json to domain Value. 4 tests.
rss: XML RSS feed parser, extracts items into Value array. 1 test.
media: Navidrome/Subsonic getNowPlaying adapter. 2 tests with fake server.

crates/adapters/http-json/tests/http_json_tests.rs

@@ -0,0 +1,102 @@
+use std::time::Duration;
+use axum::{Router, routing::get, response::Json};
+use domain::{DataSource, DataSourceConfig, DataSourcePort, DataSourceType, Value};
+use http_json::HttpJsonAdapter;
+
+async fn start_fake_api() -> String {
+    let app = Router::new()
+        .route("/weather", get(|| async {
+            Json(serde_json::json!({
+                "main": {"temp": 5.4, "humidity": 80},
+                "weather": [{"icon": "cloud_rain"}]
+            }))
+        }))
+        .route("/simple", get(|| async {
+            Json(serde_json::json!({"value": "hello"}))
+        }))
+        .route("/not-json", get(|| async { "plain text" }));
+
+    let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr = listener.local_addr().unwrap();
+    tokio::spawn(async move {
+        axum::serve(listener, app).await.unwrap();
+    });
+    format!("http://{addr}")
+}
+
+fn make_source(url: String) -> DataSource {
+    DataSource {
+        id: 1,
+        name: "test".into(),
+        source_type: DataSourceType::HttpJson,
+        poll_interval: Duration::from_secs(60),
+        config: DataSourceConfig {
+            url: Some(url),
+            headers: vec![],
+            api_key: None,
+        },
+    }
+}
+
+#[tokio::test]
+async fn polls_url_and_returns_nested_json_as_value() {
+    let base = start_fake_api().await;
+    let adapter = HttpJsonAdapter::new();
+    let source = make_source(format!("{base}/weather"));
+
+    let result = adapter.poll(&source).await.unwrap();
+
+    assert_eq!(
+        result.get_path("$.main.temp"),
+        Some(&Value::Number(5.4))
+    );
+    assert_eq!(
+        result.get_path("$.main.humidity"),
+        Some(&Value::Number(80.0))
+    );
+    assert_eq!(
+        result.get_path("$.weather[0].icon"),
+        Some(&Value::String("cloud_rain".into()))
+    );
+}
+
+#[tokio::test]
+async fn polls_simple_json() {
+    let base = start_fake_api().await;
+    let adapter = HttpJsonAdapter::new();
+    let source = make_source(format!("{base}/simple"));
+
+    let result = adapter.poll(&source).await.unwrap();
+    assert_eq!(
+        result.get_path("$.value"),
+        Some(&Value::String("hello".into()))
+    );
+}
+
+#[tokio::test]
+async fn returns_error_when_no_url() {
+    let adapter = HttpJsonAdapter::new();
+    let source = DataSource {
+        id: 1,
+        name: "bad".into(),
+        source_type: DataSourceType::HttpJson,
+        poll_interval: Duration::from_secs(60),
+        config: DataSourceConfig {
+            url: None,
+            headers: vec![],
+            api_key: None,
+        },
+    };
+
+    let result = adapter.poll(&source).await;
+    assert!(result.is_err());
+}
+
+#[tokio::test]
+async fn returns_error_on_connection_refused() {
+    let adapter = HttpJsonAdapter::new();
+    let source = make_source("http://127.0.0.1:1".into());
+
+    let result = adapter.poll(&source).await;
+    assert!(result.is_err());
+}