Allow overriding Docker base image

Dockerfile

@@ -1,4 +1,5 @@
-FROM python:3.12-slim
+ARG PYTHON_IMAGE=python:3.12-slim
+FROM ${PYTHON_IMAGE}
 
 LABEL maintainer='<author>'
 LABEL version='0.0.0-dev.0-build.0'

docker-compose.yml

@@ -1,7 +1,9 @@
-version: '3'
 services:
   webssh:
-    build: .
+    build:
+      context: .
+      args:
+        PYTHON_IMAGE: ${PYTHON_IMAGE:-python:3.12-slim}
     restart: unless-stopped
     ports:
       - "8888:8888"