Consider how to handle ImageStreams from openshift namespace relevant to migrations

> Customer asks me for ImageStreams located in the namespace Openshift that are used as base images in BuildConfigs in the namespace of the application. These are neither cluster-wide resources, nor resources of the migrated namespace, although they are needed by the application.

> There is another use case: Most of the customers have a department that certifies images and even modify them slightly to add a monitorization layer or some environment variables, etc. They normally create new IS in the Openshift environment to allow developers to access those IS and build their applications using those base images instead of the default ones. In this case, having some kind of analysis of the used images in BuildConfigs would be very interesting.

A few use cases have been brought to our attention that are possible gaps. We ignore the images found inside of the openshift namespace, but there are legitimate use cases we should consider here.

• Maybe ensure we warn a customer if an image from 'openshift' namespace is being used and is not available from the destination cluster?