BAEL-8824 Align module names, folder names and artifact id

- Folder name changes

spring-5-data-reactive/src/main/kotlin/com/baeldung/Application.kt

@@ -0,0 +1,11 @@
+package com.baeldung
+
+import org.springframework.boot.SpringApplication
+import org.springframework.boot.autoconfigure.SpringBootApplication
+
+@SpringBootApplication
+class Application
+
+fun main(args: Array<String>) {
+    SpringApplication.run(Application::class.java, *args)
+}