Add Docker and CI build

.gitlab-ci.yml

+stages:
+ - lint
+ - build
+ - test
+ - cleanup
+
+docker-setup-and-processing-build:
+  stage: build
+  image: docker:24.0.6
+  services:
+    - docker:24.0.6-dind
+  script:
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
+    - docker build -f Dockerfile.minimal -t ${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHORT_SHA} -t ${CI_REGISTRY_IMAGE}:latest .
+    - docker push --all-tags ${CI_REGISTRY_IMAGE}
+  tags:
+    - public-runner-docker

Dockerfile.minimal

+FROM python:3.6.9-slim as base
+
+# Setup env
+ENV LANG C.UTF-8
+ENV LC_ALL C.UTF-8
+ENV PYTHONDONTWRITEBYTECODE 1
+ENV PYTHONFAULTHANDLER 1
+
+FROM base AS python-deps
+
+# Install pipenv and compilation dependencies
+RUN pip install pipenv
+RUN apt-get update && apt-get install -y --no-install-recommends build-essential
+
+# Install python dependencies in /.venv
+COPY Pipfile .
+COPY Pipfile.lock .
+RUN PIPENV_VENV_IN_PROJECT=1 pipenv install --deploy
+
+FROM base AS runtime
+
+# Copy virtual env from python-deps stage
+COPY --from=python-deps /.venv /.venv
+ENV PATH="/.venv/bin:$PATH"
+
+## Create and switch to a new user
+RUN useradd --create-home jussi
+WORKDIR /home/jussi
+USER jussi
+
+# Install application into container
+COPY . .
+
+# Run the application
+ENTRYPOINT ["python", "-m", "jussi.serve"]
+CMD []