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/pipelines/container-build.yaml

@@ -0,0 +1,99 @@
+apiVersion: tekton.dev/v1beta1
+kind: Pipeline
+metadata:
+  name: container-build
+  namespace: innoventions
+  labels:
+    app.kubernetes.io/version: "0.1"
+  annotations:
+    tekton.dev/pipelines.minVersion: "0.29.0"
+    tekton.dev/categories: Container Build
+    tekton.dev/tags: git, kaniko, build
+    tekton.dev/displayName: "Container Build Pipeline"
+spec:
+  description: >-
+    This pipeline clones a git repository and builds a container image from it using Kaniko.
+    
+    The pipeline performs the following steps:
+    1. Clone the git repository to a shared workspace
+    2. Build and push the container image to Harbor registry
+
+  params:
+    - name: git-url
+      type: string
+      description: The git repository URL to clone
+    - name: git-revision
+      type: string
+      description: The git revision (branch, tag, sha) to checkout
+      default: "main"
+    - name: image-name
+      type: string
+      description: The complete image name including registry (e.g., the-seas.local.mk-labs.cloud/library/app)
+    - name: image-tag
+      type: string
+      description: The image tag to apply
+      default: "latest"
+    - name: dockerfile
+      type: string
+      description: Path to the Dockerfile relative to the repository root
+      default: "./Dockerfile"
+    - name: context
+      type: string
+      description: Path to the build context relative to the repository root
+      default: "./"
+
+  workspaces:
+    - name: shared-workspace
+      description: |
+        This workspace will hold the cloned git repository and is shared between tasks.
+        It should be backed by a PersistentVolumeClaim or VolumeClaimTemplate.
+    - name: docker-credentials
+      description: |
+        This workspace contains the docker config.json for authenticating to Harbor.
+        It should be backed by a Secret containing .dockerconfigjson
+
+  tasks:
+    - name: fetch-repository
+      taskRef:
+        name: git-clone
+      workspaces:
+        - name: output
+          workspace: shared-workspace
+      params:
+        - name: url
+          value: $(params.git-url)
+        - name: revision
+          value: $(params.git-revision)
+        - name: deleteExisting
+          value: "true"
+
+    - name: build-and-push
+      taskRef:
+        name: kaniko-build
+      runAfter:
+        - fetch-repository
+      workspaces:
+        - name: source
+          workspace: shared-workspace
+        - name: dockerconfig
+          workspace: docker-credentials
+      params:
+        - name: IMAGE
+          value: "$(params.image-name):$(params.image-tag)"
+        - name: DOCKERFILE
+          value: $(params.dockerfile)
+        - name: CONTEXT
+          value: $(params.context)
+        - name: EXTRA_ARGS
+          value:
+            - --skip-tls-verify
+            - --verbosity=info
+            - --skip-unused-stages=true
+
+  results:
+    - name: IMAGE_DIGEST
+      description: The digest of the built image
+      value: $(tasks.build-and-push.results.IMAGE_DIGEST)
+    - name: IMAGE_URL
+      description: The URL of the built image
+      value: $(tasks.build-and-push.results.IMAGE_URL)