fix #3645 #2838 migration guide entries for the api split/repackaging

doc/MIGRATION-v6.md

@@ -1,8 +1,29 @@
 # Migration from 5.x to 6.x
 
 ## Contents:
+- [API/Impl split](#api-impl-split)
+- [Deprecation Removals](#deprecation-removals)
 - [IntOrString changes](#intorstring-changes)
 
+## API/Impl split
+
+This release introduces kubernetes-client-api and openshift-client-api modules.  You may use them as compile dependencies in your application with the respective kubernetes-client and openshift-client as runtime dependencies.  This will keep you compile classpath cleaner of classes and libraries that are not intentionally exposed by the fabric8 client.
+
+If you are directly relying on classes in the -client jars other than DefaultKubernetesClient and DefaultOpenShiftClient, please let us know your usage scenario.  Moving forward we'd like consider all classes in the -client jars internal.
+
+When you rely solely on a compile dependency to the respective -api dependencies you will not be able to use DefaultKubernetesClient nor DefaultOpenShiftClient directly to create your client instances.  You should instead - TBD 
+
+### Package Changes
+
+- Readiness/OpenShiftReadiness moved from client.internal.readiness to client.readiness
+- client.utils classes including Base64, CreateOrReplaceHelper, DeleteOrCreateHelper, OptionalDendencyWrapper, etc. are not in the -api jar, they are still in the -client jar under utils.internal.
+- Some other effectively internal classes in dsl.base and other packages were moved to corresponding internal packages - it is unlikely this will affect you unless you developed a custom extension.
+
+## Deprecation Removals
+
+- Removed KubernetesClient.customResource / RawCustomResourceOperationsImpl, please use the generic resource api instead 
+- Removed deprecatedHttpClientUtils.createHttpClient(final Config config, final Consumer<OkHttpClient.Builder> additionalConfig), please use the OkHttpClientFactory instead
+- Removed deprecated methods on SharedInformerFactory dealing with the OperationContext
 
 ## IntOrString changes