Support STACK_NAME / PHP_SERVICE..

..so it continues to work on both local and remote

Dockerfile

@@ -1,4 +1,17 @@
 FROM nginx:1.21.4
 # TODO: use renovate-bot to send pull requests on upstream image updates
 
-COPY nginx.conf /etc/nginx/templates/default.conf.template
+RUN mkdir /etc/nginx/templates.override
+COPY nginx.conf /etc/nginx/templates.override/default.conf.template
+
+# goenvtemplator2 for config file updates, working around msmtp's inability to
+# configure itself from environment variables.
+# nginx includes gettext's envsubst, which is generall is more common, but it
+# doesn't support conditionals, or even the "default" syntax ${FOO:+default}
+ADD https://github.com/seznam/goenvtemplator/releases/download/v2.0.0/goenvtemplator2-amd64 /usr/local/bin/goenvtemplator2
+RUN chmod +x /usr/local/bin/goenvtemplator2
+
+COPY entrypoint.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
+ENTRYPOINT [ "/usr/local/bin/entrypoint.sh" ]
+CMD ["nginx", "-g", "daemon off;"]