Add example for 'podman play kube'

samples/casdk-demo/README.md

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+# Carbon Aware SDK demonstration on Podman
+
+This folder contains an example for Carbon Aware SDK and Swagger UI for the SDK. The user can demonstrate Carbon Aware SDK via Swagger UI with just one command.
+
+This demonstration uses `podman play kube` to deploy apps like a Kubernetes application. Deployment is defined in [demo.yaml](demo.yaml).
+
+## Requirements
+
+- Podman
+
+## Ports to open
+
+Podman creates virtual network, then all of containers in the deployment would be located flatten. So Each containers can access each other as a `localhost`. We need to consider TCP port:
+
+* 8080: Carbon Aware SDK
+* 8081: Swagger UI
+* 8082: NGINX (for reverse proxy)
+
+NGINX is a reverse proxy to both Carbon Aware SDK and Swagger UI. To avoid CORS error, you can access Swagger UI via NGINX ( http://localhost:8082/swagger-ui/ ).
+
+## Reverse proxy rule
+
+See [nginx-rp.conf](nginx-rp.conf)
+
+/ -> Carbon Aware SDK  
+/swagger.yaml -> OpenAPI document provided by Carbon Aware SDK  
+/swagger-ui/ -> Swagger UI for Carbon Aware SDK
+
+## How to run
+
+1. Set environment variables prefixed with `CASDK_`: e.g. `CASDK_DataSources__EmissionsDataSource`
+
+2. Start demonstration
+
+```
+./demo.sh start
+```
+
+:::warning
+
+* [demo.sh](demo.sh) would create `/tmp/casdk-config.yaml` which may contain credentials (e.g. API token of backend service). This file would be removed by `./demo.sh stop`.
+* [demo.sh](demo.sh) would change security context of [nginx-rp.conf](nginx-rp.conf) to `container_file_t` if SELinux is enabled. It would not recover in `./demo.sh stop`, so you need to recover manually via `restorecon` if need.
+
+:::
+
+3. Access endpoints (e.g. http://localhost:8082/swagger-ui/ )
+
+4. Stop demonstration
+
+```
+./demo.sh stop
+```
+
+## Example
+
+Run demonstration with ElectricityMapsFree datasource
+
+```
+export CASDK_DataSources__EmissionsDataSource=ElectricityMapsFree
+export CASDK_DataSources__Configurations__ElectricityMapsFree__Type=ElectricityMapsFree
+export CASDK_DataSources__Configurations__ElectricityMapsFree__token=YOUR_SECRET_TOKEN
+
+./demo.sh start
+```

samples/casdk-demo/casdk-config.yaml.template

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+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: casdk-config
+data:
+  # Environment variables would be added by demo.sh

samples/casdk-demo/demo.sh

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+#!/bin/sh
+
+THISFILE=$0
+BASEDIR=$(dirname $THISFILE)
+SUBCMD=$1
+CONFIGMAP=/tmp/casdk-config.yaml
+
+help_and_exit () {
+  echo "Usage:"
+  echo "  $THISFILE [start|stop]"
+
+  rm -f $CONFIGMAP
+  exit 1
+}
+
+start () {
+  # Create ConfigMap for envvars in CASDK container
+  cp -f $BASEDIR/casdk-config.yaml.template $CONFIGMAP
+  for CASDK_ENV in `env | grep CASDK_`; do
+    KEY=`echo $CASDK_ENV | cut -d '=' -f 1 | sed -e 's/^CASDK_//'`
+    VALUE=`echo $CASDK_ENV | cut -d '=' -f '2'`
+
+    echo "  $KEY: $VALUE" >> $CONFIGMAP
+  done
+
+
+  # Change security context of nginx-rp.conf because it would be mounted by
+  # NGINX container in demo.yaml.
+  SELINUX_MODE=`getenforce 2>/dev/null`
+  if [ "$SELINUX_MODE" = 'Enforcing' ]; then
+    chcon -t container_file_t $BASEDIR/nginx-rp.conf
+  fi
+
+  # Start Podman
+  # Move to BASEDIR because demo.yaml should refer nginx-rp.conf in that dir.
+  pushd $BASEDIR > /dev/null 2>&1
+  podman play kube --configmap=$CONFIGMAP demo.yaml
+  popd > /dev/null 2>&1
+}
+
+stop () {
+  podman play kube --down $BASEDIR/demo.yaml
+  rm -f $CONFIGMAP
+}
+
+case "$SUBCMD" in
+  start)
+    start;;
+
+  stop)
+    stop;;
+
+  *)
+    help_and_exit;;
+esac

samples/casdk-demo/demo.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: casdk-demo
+  labels:
+    app: casdk-demo
+spec:
+  selector:
+    matchLabels:
+      app: casdk-demo
+  template:
+    metadata:
+      labels:
+        app: casdk-demo
+    spec:
+      containers:
+      - name: carbon-aware-sdk
+        image: ghcr.io/green-software-foundation/carbon-aware-sdk:pre
+        envFrom:
+        - configMapRef:
+            name: casdk-config
+        ports:
+        - containerPort: 8080
+          hostPort: 8080
+      - name: swagger-ui
+        image: swaggerapi/swagger-ui
+        env:
+        - name: SWAGGER_JSON_URL
+          value: /swagger.yaml
+        - name: PORT
+          value: "8081"
+        ports:
+        - containerPort: 8081
+          hostPort: 8081
+      - name: nginx
+        image: nginx
+        ports:
+        - containerPort: 8082
+          hostPort: 8082
+        volumeMounts:
+        - name: rp-config
+          mountPath: /etc/nginx/conf.d/default.conf
+      volumes:
+      - name: rp-config
+        hostPath:
+          path: nginx-rp.conf
+          type: File

samples/casdk-demo/nginx-rp.conf

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+server {
+  listen 8082;
+
+  location / {
+    proxy_pass http://localhost:8080;
+  }
+
+  location /swagger.yaml {
+    proxy_pass http://localhost:8080/api/v1/swagger.yaml;
+  }
+
+  location /swagger-ui/ {
+    proxy_pass http://localhost:8081/;
+  }
+
+}