Merge branch 'docker-build-alpine' into 'main'

Switch base image to alpine, install updates and perform cleanup

See merge request clay/ddns-cloudflare!10

Dockerfile

@@ -1,16 +1,19 @@
 # Use an official Python runtime as a parent image
-FROM python:3.12-slim
+FROM python:3.12-alpine
 
 # Set the working directory in the container
 WORKDIR /app
 
 # Copy the current directory contents into the container at /app
 COPY . /app
 
-# Install any needed packages specified in requirements.txt
-RUN pip install --no-cache-dir -r requirements.txt
+# Install available updates and python packages from requirements.txt
+RUN set -ex \
+    && apk upgrade --available --no-cache \
+    && rm -rf /var/cache/apk/* \
+    && pip install --no-cache-dir -r requirements.txt \
+    && pip cache purge
 
-# Make port 80 available to the world outside this container
 EXPOSE 8080
 
 # Allow stdout from python app through to docker logs