fix: Improve error logging in case of connection failure (#367)

Closes #363.

src/main/java/it/mulders/mcs/search/SearchClient.java

@@ -4,6 +4,7 @@
 import it.mulders.mcs.common.SearchResponseBodyHandler;
 
 import java.io.IOException;
+import java.net.ConnectException;
 import java.net.URI;
 import java.net.http.HttpClient;
 import java.net.http.HttpRequest;
@@ -32,6 +33,9 @@ public Result<SearchResponse> search(final SearchQuery query) {
         try {
             return client.send(request, new SearchResponseBodyHandler())
                     .body();
+        } catch (ConnectException e) {
+            // The JDK HTTP client throws a ConnectException without a message, we can do better.
+            return new Result.Failure<>(new ConnectException("Can't resolve " + hostname));
         } catch (IOException | InterruptedException e) {
             return new Result.Failure<>(e);
         }

src/test/java/it/mulders/mcs/search/SearchClientIT.java

@@ -129,6 +129,7 @@ void should_gracefully_handle_connection_failure() {
 
             assertThat(result).isInstanceOf(Result.Failure.class);
             assertThat(result.cause()).isInstanceOf(ConnectException.class);
+            assertThat(result.cause().getLocalizedMessage()).contains("localhost:21");
         }
     }
 }