Container name should not be generated from maven group Id

[ChrisShain]

Description

When generating Kubernetes configurations, if username is omitted then maven group Id is inserted instead. Maven group id's often have periods, which are illegal characters in Kubernetes container names. Therefore, defaulting to an unmodified group ID seems like the wrong thing to do. Either remove the periods, or default to something else.

The erroneous function is extractContainerName in KubernetesResourceUtil. Decompiled, roughly:

    private static String extractImageUser(String image, MavenProject project) {
        ImageName name = new ImageName(image);
        String imageUser = name.getUser();
        return imageUser != null ? imageUser : project.getGroupId();
    }

Info

• f-m-p version : 3.5.40
• Maven version (mvn -v) : Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-10T11:41:47-05:00)

• Kubernetes / OpenShift setup and version : minikube version: v0.27.0
• If it's a bug, how to reproduce : create a maven project with a period in the group Id, and configure the plugin as follows:

                <configuration>
                    <registry>registry.gitlab.com/deltavstudios/flightcontrol</registry>
                    <images>
                        <image>
                            <!-- I am using a private registry here -->
                            <name>192.168.99.100:32449/%a:%l</name>
                            <build>
                               <!-- whatever -->
                            </build>
                        </image>
                    </images>
                </configuration>