feat(image): Add Dockerfile

# Issue

The `devxci/mbtci-java21-node22` image does not contain the tools
necessary to build and scan Python-based apps.
On the other hand the image already contains all tools to run `mbt` and
perform scans using `piper`.

# Fix

Add `python3`, `pip` and `pipx` to image to enable building and scanning
Python-based apps.

.github/workflows/build-image.yaml

@@ -0,0 +1,34 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true # ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
+          tags: ghcr.io/${{ github.repository }}:latest

Dockerfile

@@ -0,0 +1,18 @@
+# Use the base image
+FROM devxci/mbtci-java21-node22
+
+ARG MTA_USER="mta"
+
+# Switch to root user to install packages
+USER root
+
+# Install python3, pip, pipx
+RUN apt-get update && \
+    apt-get install -y python3 python3-pip python3-venv && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/* && \
+    pip install pipx && \
+    python3 --version && pip --version && pipx --version
+
+# Switch back to the original user
+USER ${MTA_USER}