Add startup checks

src/main/java/com/petshop/backend/BackendApplication.java

@@ -9,6 +9,7 @@ import org.springframework.data.web.config.EnableSpringDataWebSupport;
 @EnableSpringDataWebSupport(pageSerializationMode = EnableSpringDataWebSupport.PageSerializationMode.VIA_DTO)
 public class BackendApplication {
     public static void main(String[] args) {
+        RuntimeClasspathValidator.validate();
         new SpringApplicationBuilder(BackendApplication.class)
                 .initializers(new FlywayContextInitializer())
                 .run(args);