WIP: Draft version of the advanced routing demo

Just getting all the content in one place. Need some refactoring to a sample vs a demo script.

serving/samples/blue-green-deployment

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+# Advanced deploy (aka blue/green)
+
+Simple blue/green-like application deployment pattern illustrating process of updating live application without dropping any traffic. 
+
+> Note, this demo assumes you mapped domain to your cluster. For purposes of this demo we will use `project-serverless.com`. Substitude with your own domain. 
+
+## Deploy app (blue)
+
+First the initial version of the applicaiton (blue). Save the beloow manifest as `stage1.yaml`
+
+```yaml
+apiVersion: serving.knative.dev/v1alpha1
+kind: Route
+metadata:
+  name: route-demo
+  namespace: default
+spec:
+  traffic:
+  - configurationName: route-demo-config-v1
+    percent: 100
+---
+apiVersion: serving.knative.dev/v1alpha1
+kind: Configuration
+metadata:
+  name: route-demo-config-v1
+  namespace: default
+spec:
+  revisionTemplate:
+    metadata:
+      labels:
+        knative.dev/type: container
+    spec:
+      container:
+        image: gcr.io/knative-samples/knative-route-demo:blue
+        imagePullPolicy: Always
+        env:
+          - name: T_VERSION
+            value: "blue"
+ ```
+
+And then apply that manifest. 
+
+`kubectl apply -f stage1.yaml`
+
+When route created and IP assigned, navigate to http://route-demo.default.project-serverless.com to show deployed app. Let's call this blue (aka v1) version of the app.
+
+## Deploy new (green) version of the app
+
+Again, save the following manifest representing application update to `stage2.yaml`
+
+```yaml
+apiVersion: serving.knative.dev/v1alpha1
+kind: Route
+metadata:
+  name: route-demo
+  namespace: default
+spec:
+  traffic:
+  - configurationName: route-demo-config-v1
+    percent: 100
+  - configurationName: route-demo-config-v2
+    percent: 0
+    name: v2
+---
+apiVersion: serving.knative.dev/v1alpha1
+kind: Configuration
+metadata:
+  name: route-demo-config-v2
+  namespace: default
+spec:
+  revisionTemplate:
+    metadata:
+      labels:
+        knative.dev/type: container
+    spec:
+      container:
+        image: gcr.io/knative-samples/knative-route-demo:green
+        imagePullPolicy: Always
+        env:
+          - name: T_VERSION
+            value: "green"
+```
+
+And then apply that file to your cluster
+
+`kubectl apply -f stage2.yaml`
+
+This will only stage v2. That means:
+
+* Won't route any of v1 (blue) traffic to that new (green) version, and
+* Create new named route (`v2`) for testing of new the newlly deployed version
+
+Refresh v1 (http://route-demo.default.project-serverless.com) to show our v2 takes no traffic,
+and navigate to http://v2.route-demo.default.project-serverless.com to show the new `v2` named route.
+
+## Migrate portion of v1 (blew) traffic to v2 (green)
+
+Now we are going to migrate traffic. Save this manofest to `stage3.yaml`
+
+```yaml
+apiVersion: serving.knative.dev/v1alpha1
+kind: Route
+metadata:
+  name: route-demo
+  namespace: default
+spec:
+  traffic:
+  - configurationName: route-demo-config-v1
+    percent: 50
+  - configurationName: route-demo-config-v2
+    percent: 50
+    name: v2
+```
+
+And then apply it
+
+`kubectl apply -f stage3.yaml`
+
+Refresh (a few times) the original route http://route-demo.default.project-serverless.com to show part of traffic going to v2
+
+> Note, demo uses 50/50 split to assure you don't have to refresh too much, normally you would start with 1-2% maybe
+
+## Re-route 100% of traffic to v2 (green)
+
+Finally, we will migeate all traffic to the green version. Save the following manofest to `stage4.yaml`
+
+```yaml
+apiVersion: serving.knative.dev/v1alpha1
+kind: Route
+metadata:
+  name: route-demo
+  namespace: default
+spec:
+  traffic:
+  - configurationName: route-demo-config-v1
+    percent: 0
+    name: v1
+  - configurationName: route-demo-config-v2
+    percent: 100
+```
+
+`kubectl apply -f stage4.yaml`
+
+This will complete the deployment by sending all traffic to the new (green) version.
+
+Refresh original route http://route-demo.default.project-serverless.com bunch of times to show that all traffic goes to v2 (green) and v1 (blue) no longer takes traffic.
+
+Optionally, I like to pointing out that:
+
+* I kept v1 (blue) entry with 0% traffic for speed of reverting, if ever necessary
+* I added named route `v1` to the old (blue) version of the app to allow access for comp reasons
+
+Navigate to http://v1.route-demo.default.project-serverless.com to show the old version accessible by `v1` named route
+
+
+## Cleanup
+
+```
+kubectl delete -f stage4.yaml --ignore-not-found=true
+kubectl delete -f stage3.yaml --ignore-not-found=true
+kubectl delete -f stage2.yaml --ignore-not-found=true
+kubectl delete -f stage1.yaml --ignore-not-found=true
+```