Add coverage for HTTP 1.0 request with no host header

http/http-advanced-reactive/src/test/java/io/quarkus/ts/http/advanced/reactive/HeadersIT.java

@@ -7,7 +7,13 @@
 import static org.hamcrest.Matchers.hasItem;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
+import static org.hamcrest.Matchers.stringContainsInOrder;
 
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.Socket;
 import java.util.List;
 
 import org.junit.jupiter.api.Tag;
@@ -16,6 +22,7 @@
 import io.quarkus.test.bootstrap.RestService;
 import io.quarkus.test.scenarios.QuarkusScenario;
 import io.quarkus.test.services.QuarkusApplication;
+import io.quarkus.test.services.URILike;
 import io.restassured.http.Header;
 import io.restassured.response.ValidatableResponse;
 
@@ -116,6 +123,27 @@ void testWithNoAcceptHeader() {
                 .body(is("Headers response: ok headers"));
     }
 
+    @Test
+    @Tag("https://github.com/quarkusio/quarkus/discussions/42636")
+    public void testHttp10WithoutHostHeader() throws InterruptedException, IOException {
+        // We can't use java client as it's always adding `\r\n` to the host header.
+        URILike uri = app.getURI();
+        StringBuilder response = new StringBuilder();
+        try (Socket s = new Socket(uri.getHost(), uri.getPort());
+                PrintWriter pw = new PrintWriter(s.getOutputStream());
+                BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));) {
+            pw.print("GET /headers/any HTTP/1.0\n\r\n");
+            pw.flush();
+            String line;
+            while ((line = br.readLine()) != null) {
+                response.append(line).append("/n");
+            }
+        }
+
+        assertThat(response.toString(), stringContainsInOrder("HTTP/1.0", "200 OK"));
+        app.logs().assertDoesNotContain("Unhandled exception in router");
+    }
+
     /**
      * Cache-Control header may be present multiple times in the response, e.g. in an OpenShift deployment. That is why we need
      * to look for a specific value among all headers of the same name, and not just match the last one of them, which is what