Adding the messagesHistory method in the OpenAiController.

Author: n-o-u-r-h-a-n

sample-code/spring-app/src/main/java/com/sap/ai/sdk/app/controllers/OpenAiController.java

@@ -45,7 +45,7 @@ Object chatCompletion(
   @Nonnull
   Object messagesHistory(
       @Nullable @RequestParam(value = "format", required = false) final String format,
-      @Nonnull @RequestParam(value = "previousMessage", defaultValue = "Who is the prettiest")
+      @Nonnull @RequestParam(value = "previousMessage", defaultValue = "What is the capital of France?")
           final String previousMessage) {
     final var response = service.messagesHistory(previousMessage);
     if ("json".equals(format)) {