BAEL-5525 add mainClass and layout configuration to the spring boot maven plugin (#13049)

* BAEL-5617 Handle classes with the same name in Java

code samples

* BAEL-5617 Handle classes with the same name in Java

update project module

* BAEL-5754 Convert a List of String to a comma-separated String

code samples

* BAEL-5754 update unit test class name

* BAEL-5754 update unit test methods naming

* BAEL-5754 update tests order so to reflect the article

* BAEL-5754 align code to article

* BAEL-5525 add mainClass and layout configuration to the spring boot maven plugin

spring-boot-modules/spring-boot-artifacts-2/pom.xml

@@ -27,6 +27,10 @@
             <plugin>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>
+                <configuration>
+                    <mainClass>com.baeldung.demo.DemoApplication</mainClass>
+                    <layout>JAR</layout>
+                </configuration>
                 <executions>
                     <execution>
                         <goals>