Add proof of principle manifest

The proof of principle shows that mlflow models can be pulled, build, and
deployed within a Kubernetes cluster in three simple steps.

proof-of-principle.yaml

+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: "mlflow-model"
+spec:
+  accessModes:
+    - ReadWriteMany
+  resources:
+    requests:
+      storage: 100Mi
+  volumeMode: Filesystem
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: test
+  name: test
+spec:
+  selector:
+    matchLabels:
+      app: test
+  template:
+    metadata:
+      labels:
+        app: test
+    spec:
+      containers:
+      - image: "python:3.10"
+        command: ["tail", "-f", "/dev/null"]
+        name: test
+        volumeMounts:
+        - mountPath: /pvc
+          name: pvc-mount
+      volumes:
+      - name: pvc-mount
+        persistentVolumeClaim:
+          claimName: mlflow-model
+---
+apiVersion: v1
+kind: Pod
+metadata:
+  name: kaniko
+spec:
+  containers:
+  - name: kaniko
+    image: gcr.io/kaniko-project/executor:latest
+    args:
+    - "--dockerfile=Dockerfile"
+    - "--context=/pvc"
+    - "--destination=gitlab.sauerburger.com:5049/frank/titanic-ml/test:2"
+    volumeMounts:
+    - name: context
+      mountPath: /pvc
+    - name: docker-secret
+      mountPath: /kaniko/.docker
+  restartPolicy: Never
+  volumes:
+  - name: context
+    persistentVolumeClaim:
+      claimName: mlflow-model
+  - name: docker-secret
+    secret:
+      secretName: titanic-ml-token
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: test-serve
+  name: test-serve
+spec:
+  selector:
+    matchLabels:
+      app: test-serve
+  template:
+    metadata:
+      labels:
+        app: test-serve
+    spec:
+      imagePullSecrets:
+      - name: titanic-ml-token
+      containers:
+      - image: gitlab.sauerburger.com:5049/frank/titanic-ml/test:2
+        name: test-serve
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: titanic-ml
+spec:
+  type: ClusterIP
+  ports:
+    - port: 8080
+      targetPort: 8080
+      protocol: TCP
+  selector:
+    app: test-serve
+---
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  annotations:
+    cert-manager.io/cluster-issuer: "letsencrypt-production"
+    kubernetes.io/ingress.class: nginx
+  name: "test-ingress"
+spec:
+  rules:
+  - host: "titanic.ds.sit-servers.net"
+    http:
+      paths:
+      - path: /
+        pathType: Prefix
+        backend:
+          service:
+            name: "titanic-ml"
+            port:
+              number: 8080
+  tls:
+  - hosts:
+    - "titanic.ds.sit-servers.net"
+    secretName: test-ingress-tls-secret