Handle non-200 HTTP status codes in AstroGateway

Added a check for non-200 HTTP status codes in AstroGateway and return a Failure with a RuntimeException. This ensures that errors are correctly handled and propagated, improving the system's robustness.

src/main/java/com/kousenit/astro/AstroGateway.java

@@ -35,6 +35,9 @@ public Result<AstroResponse> getResult() {
             HttpResponse<String> httpResponse =
                     client.send(request, HttpResponse.BodyHandlers.ofString());
             System.out.println(httpResponse.statusCode());
+            if (httpResponse.statusCode() != 200) {
+                return new Failure<>(new RuntimeException("HTTP error: " + httpResponse.statusCode()));
+            }
             return new Success<>(
                     objectMapper.readValue(httpResponse.body(), AstroResponse.class));
         } catch (IOException | InterruptedException e) {