Added e2e test

Author: CharlesDuboisSAP

sample-code/spring-app/src/test/java/com/sap/ai/sdk/app/controllers/PromptRegistryTest.java

@@ -0,0 +1,15 @@
+package com.sap.ai.sdk.app.controllers;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+public class PromptRegistryTest {
+
+    @Test
+    void listTemplates() {
+        var controller = new PromptRegistryController();
+        var result = controller.listTemplates();
+        assertThat(result.getCount()).isGreaterThan(0);
+    }
+}