fix: [Orchestration] default values for template messages (#391)

* Initial

* Add test assertion

---------

Co-authored-by: Alexander Dümont <[email protected]>

Author: newtork

orchestration/src/main/java/com/sap/ai/sdk/orchestration/ConfigToRequestTransformer.java

@@ -51,20 +51,30 @@ static TemplatingModuleConfig toTemplateModuleConfig(
     if (config instanceof TemplateRef) {
       return config;
     }
+
     val template = config instanceof Template t ? t : Template.create().template();
     val messages = template.getTemplate();
     val responseFormat = template.getResponseFormat();
     val messagesWithPrompt = new ArrayList<>(messages);
+
     messagesWithPrompt.addAll(
         prompt.getMessages().stream().map(Message::createChatMessage).toList());
     if (messagesWithPrompt.isEmpty()) {
       throw new IllegalStateException(
           "A prompt is required. Pass at least one message or configure a template with messages or a template reference.");
     }
-    return Template.create()
-        .template(messagesWithPrompt)
-        .tools(template.getTools())
-        .responseFormat(responseFormat);
+
+    val result =
+        Template.create()
+            .template(messagesWithPrompt)
+            .tools(template.getTools())
+            .defaults(template.getDefaults())
+            .responseFormat(responseFormat);
+
+    for (val customFieldName : template.getCustomFieldNames()) {
+      result.setCustomField(customFieldName, template.getCustomField(customFieldName));
+    }
+    return result;
   }
 
   @Nonnull

orchestration/src/test/java/com/sap/ai/sdk/orchestration/ConfigToRequestTransformerTest.java

@@ -62,12 +62,16 @@ void testMergingTemplateConfig() {
                 List.of(
                     systemMessage.createChatMessage(),
                     userMessage.createChatMessage(),
-                    userMessage2.createChatMessage()));
+                    userMessage2.createChatMessage()))
+            .defaults(Map.of("city", "Paris"));
+    expected.setCustomField("country", "France");
 
     var prompt = new OrchestrationPrompt(userMessage2);
     var templateConfig =
         Template.create()
-            .template(List.of(systemMessage.createChatMessage(), userMessage.createChatMessage()));
+            .template(List.of(systemMessage.createChatMessage(), userMessage.createChatMessage()))
+            .defaults(Map.of("city", "Paris"));
+    templateConfig.setCustomField("country", "France");
     var actual = ConfigToRequestTransformer.toTemplateModuleConfig(prompt, templateConfig);
 
     assertThat(actual).isEqualTo(expected);