Extend tests

Author: rpanackal

foundation-models/openai/src/main/java/com/sap/ai/sdk/foundationmodels/openai/OpenAiChatCompletionResponse.java

@@ -75,7 +75,7 @@ public String getContent() {
    */
   @Nonnull
   public OpenAiAssistantMessage getMessage() {
-    var toolCalls = getChoice().getMessage().getToolCalls();
+    final var toolCalls = getChoice().getMessage().getToolCalls();
 
     if (toolCalls == null) {
       return OpenAiMessage.assistant(getContent());

foundation-models/openai/src/test/java/com/sap/ai/sdk/foundationmodels/openai/OpenAiClientGeneratedTest.java

@@ -593,6 +593,11 @@ void chatCompletionResponseGetMessage() {
 
     assertThat(simpleMessage).isNotNull();
     assertThat(simpleMessage.toolCalls()).isEmpty();
+    assertThat(simpleMessage.content().items()).hasSize(1);
+    assertThat(simpleMessage.content().items().get(0)).isInstanceOf(OpenAiTextItem.class);
+    assertThat(((OpenAiTextItem) simpleMessage.content().items().get(0)).text())
+        .isEqualTo(
+            "I'm an AI and cannot answer that question as beauty is subjective and varies from person to person.");
 
     stubForChatCompletionTool();