Notify user if plugin doesn't find a valid config

[lstocchi]

The k8s plugin assumes that the kube config can be found in the default path ~/.kube/config which is fine but we need to notify the user if that is not true. Otherwise they can be lost. No message, no notification and they don't know which is the problem.

The issue is that we take the path but we do not check if it really exists

intellij-kubernetes/src/main/kotlin/com/redhat/devtools/intellij/kubernetes/model/ClientConfig.kt

Lines 108 to 109 in 30c3c61

	val path = Paths.get(ConfigHelper.getKubeConfigPath())
	executors.submit(ConfigWatcher(path, ::onConfigChange))

and the getKubeConfigPath() does

public static String getKubeConfigPath() {
      return System.getProperty("user.home") + "/.kube/config";
}

Now the problem can be of two types. The user used to start IJ. E.g. In my case i have the config inside home/luca/.kube/config but if i start IJ as root then the path where the plugin will look at is root/.kube/config. Or if the config has been moved to another path.

We should tell the user why the plugin window is empty.

[adietish]

@lstocchi thx for reporting!
this is related or even duplicate to #209. Keeping this issue because of all the details that it contains.

[adietish]

this is part of the epic #208

[adietish]

This is duplicate to #817.

Closing as DUPLICATE.