Guide: Migrate from WildFly docker image to the builder/runtime images

[jmesnil]

We have many users that use https://github.com/jboss-dockerfiles/wildfly as the base image where they can drop their deployments.

However some new features of WildFly are only available as Galleon feature packs (Keycloak SAML adapter, gRPC, datasources), this image is not ideal to provision them on top of the base WildFly server.

We could create a guide that helps use move from the WildFly Docker image to the builder/runtime image.
The guide would explain the differences between the 2 architectures and shows how users can achieve the same application image from one architecture to another.
Then, the guide would show how you can simply add a feature pack to WildFly (eg Keycloal SAML adapter) by tweaking the Containerfile
Finally, for users that are in control of the deployment source code, we should mention that the wildfly-maven-plugin is able to generated an application image from their Maven pom.xml directly