Add Tekton tasks, pipeline and test Dockerfile

- Add git-clone task for repository cloning
- Add kaniko-build task for container image builds
- Add container-build pipeline orchestrating clone + build
- Add harbor-credentials ExternalSecret for innoventions namespace
- Add test-app.Dockerfile for pipeline validation

Day 3 deliverables for Tekton Phase 2

cluster/tekton/tasks/kaniko-build.yaml

@@ -0,0 +1,69 @@
+apiVersion: tekton.dev/v1beta1
+kind: Task
+metadata:
+  name: kaniko-build
+  namespace: innoventions
+  labels:
+    app.kubernetes.io/version: "0.1"
+  annotations:
+    tekton.dev/pipelines.minVersion: "0.29.0"
+    tekton.dev/categories: Image Build
+    tekton.dev/tags: image-build, kaniko
+    tekton.dev/displayName: "kaniko build"
+    tekton.dev/platforms: "linux/amd64,linux/arm64"
+spec:
+  description: >-
+    This Task builds source into a container image using Google's Kaniko tool.
+
+    Kaniko doesn't depend on a Docker daemon and executes each command within a Dockerfile
+    completely in userspace. This enables building container images in environments that
+    can't easily or securely run a Docker daemon, such as a standard Kubernetes cluster.
+
+  params:
+    - name: IMAGE
+      description: Name (reference) of the image to build.
+    - name: DOCKERFILE
+      description: Path to the Dockerfile to build.
+      default: ./Dockerfile
+    - name: CONTEXT
+      description: The build context used by Kaniko.
+      default: ./
+    - name: EXTRA_ARGS
+      type: array
+      default: []
+    - name: BUILDER_IMAGE
+      description: The image on which builds will run (default is v1.23.2)
+      default: gcr.io/kaniko-project/executor:v1.23.2@sha256:7f77bc1c6b96e5da7fdb56fb0dc1c16ba0f7fc8b5d1eeaa75fa5db39ec2f4a4d
+  workspaces:
+    - name: source
+      description: Holds the context and Dockerfile
+    - name: dockerconfig
+      description: Includes a docker `config.json`
+      optional: true
+      mountPath: /kaniko/.docker
+  results:
+    - name: IMAGE_DIGEST
+      description: Digest of the image just built.
+    - name: IMAGE_URL
+      description: URL of the image just built.
+  steps:
+    - name: build-and-push
+      workingDir: $(workspaces.source.path)
+      image: $(params.BUILDER_IMAGE)
+      args:
+        - $(params.EXTRA_ARGS)
+        - --dockerfile=$(params.DOCKERFILE)
+        - --context=$(workspaces.source.path)/$(params.CONTEXT)
+        - --destination=$(params.IMAGE)
+        - --digest-file=$(results.IMAGE_DIGEST.path)
+      # kaniko assumes it is running as root, which means this example fails on platforms
+      # that default to run containers as random uid (like OpenShift). Adding this securityContext
+      # makes it explicit that it needs to run as root.
+      securityContext:
+        runAsUser: 0
+    - name: write-url
+      image: docker.io/library/bash:5.1.4@sha256:c523c636b722339f41b6a431b44588ab2f762c5de5ec3bd7964420ff982fb1d9
+      script: |
+        set -e
+        image="$(params.IMAGE)"
+        echo -n "${image}" | tee "$(results.IMAGE_URL.path)"