Add a warning about missing -parameters flag for javac

Without this warning, users can end up with only an
 error complaining about a duplicate null key

core/deployment/src/main/java/io/quarkiverse/langchain4j/deployment/AiServicesProcessor.java

@@ -22,6 +22,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
@@ -946,6 +947,11 @@ private List<TemplateParameterInfo> gatherTemplateParamInfo(List<MethodParameter
             templateParams.add(new TemplateParameterInfo(0, "it"));
         }
 
+        if (templateParams.stream().map(TemplateParameterInfo::name).allMatch(Objects::isNull)) {
+            log.warn(
+                    "The application has been compiled without the '-parameters' being set flag on javac. Make sure your build tool is configured to pass this flag to javac, otherwise Quarkus LangChain4j is unlikely to work properly without it.");
+        }
+
         return templateParams;
     }