fix: missing role in api response

Author: sinedied

src/backend-java-quarkus/src/main/java/ai/azure/openai/rag/workshop/backend/rest/ChatMessage.java

@@ -3,5 +3,6 @@
 public class ChatMessage {
 
   public String content;
+  public String role;
 
 }

src/backend-java-quarkus/src/main/java/ai/azure/openai/rag/workshop/backend/rest/ChatResponse.java

@@ -14,6 +14,7 @@ public static ChatResponse fromMessage(String message) {
     choice.index = 0;
     choice.message = new ai.azure.openai.rag.workshop.backend.rest.ChatMessage();
     choice.message.content = message;
+    choice.message.role = "assistant";
     chatResponse.choices.add(choice);
     return chatResponse;
   }