Add GET /v1/actions API call to HetznerApi client

This will allow the polling of asynchronous actions from the Hetzner API
without consuming the main rate limit of the other (main) endpoints.

Author: daniel-gray-jemmic

src/main/java/cloud/dnation/hetznerclient/HetznerApi.java

@@ -30,6 +30,17 @@
  * For full version, check <a href="https://docs.hetzner.cloud/">official documentation</a>
  */
 public interface HetznerApi {
+
+    /**
+     * Get/poll the status of an asynchronous API on the Hetzner Cloud.
+     * <p>Normally, the rate limit of this API is higher and separate from the other API calls,
+     * as it is preferred to poll the /actions endpoint to wait for an asynchronous action to complete.</p>
+     * @param actionId the ID of the action whose status you want to poll
+     * @return the full Action object, including its current status
+     */
+    @GET("/v1/actions/{id}")
+    Call<ActionResponse> getActionById(@Path("id") Long actionId);
+
     /**
      * Get all images that matches given label expression.
      *

src/test/java/cloud/dnation/hetznerclient/BasicTest.java

@@ -51,6 +51,22 @@ public static void tearDownAfterClass() throws IOException {
         ws.close();
     }
 
+    @Test
+    public void testGetActionById() throws IOException {
+        ws.enqueue(new MockResponse()
+                .setBody(resourceAsString("get-action-by-id.json"))
+        );
+        Call<ActionResponse> call = api.getActionById(603984077612933L);
+        ActionResponse result = call.execute().body();
+        assertEquals("delete_server", result.getAction().getCommand());
+        assertEquals(100, result.getAction().getProgress().intValue());
+        assertEquals("success", result.getAction().getStatus());
+        assertNull(result.getAction().getError());
+        List<IdentifiableResource> relatedResources = result.getAction().getResources();
+        assertEquals(1, relatedResources.size());
+        assertEquals(117017457L, relatedResources.get(0).getId().longValue());
+    }
+
     @Test
     public void testGetNetworkById() throws IOException {
         ws.enqueue(new MockResponse()

src/test/resources/get-action-by-id.json

@@ -0,0 +1,17 @@
+{
+  "action": {
+    "id": 603984077612933,
+    "command": "delete_server",
+    "started": "2026-01-08T17:33:08Z",
+    "finished": "2026-01-08T17:33:13Z",
+    "progress": 100,
+    "status": "success",
+    "resources": [
+      {
+        "id": 117017457,
+        "type": "server"
+      }
+    ],
+    "error": null
+  }
+}