Enable FLASK_DEBUG, if set

Adds:
- a Docker image, which can be used in both development and production
- a `docker-compose.yml` file for local development (could probably be adapted for production deployments)

Testing:
- `git checkout docker`
- `docker-compose up`
- pray 🙏
- go to http://localhost:5000

## App architecture

I added the ability to load secret config variables (`HUB_TOKEN`, `STRIPE_SECRET_KEY` etc) from files, to support [Docker Secrets](https://docs.docker.com/engine/swarm/secrets/) natively. The code should probably log an error if a specified `HUB_TOKEN_FILE` doesn't exist instead of failing silently..

## Docker architecture

This uses a multi-stage build to reduce the size of the final image -- having pipenv install to a predefined virtualenv, and then copying that over.

The compose file doesn't include a definition for a cron runner service, and I haven't tested running one yet. Here be dragons!

You can rebuild the image locally using `docker-compose build`, but this isn't required for changes to the app code, only if you edit the `Dockerfile`, or want to publish your image for use on a swarm server (in which case you will need to edit the image name to put in your own Docker hub credentials).

Currently, the image is rebuilt (should set up auto-tagging..) and published with every push to this 3wordchant/capsul-flask fork.

Reviewed-on: #2
Co-authored-by: 3wordchant <3wordchant@noreply.git.autonomic.zone>
Co-committed-by: 3wordchant <3wordchant@noreply.git.autonomic.zone>

.drone.yml

@@ -0,0 +1,13 @@
+---
+kind: pipeline
+name: publish docker image
+steps:
+  - name: build and publish
+    image: plugins/docker
+    settings:
+      username:
+        from_secret: docker_reg_username_3wc
+      password:
+        from_secret: docker_reg_passwd_3wc
+      repo: 3wordchant/capsul-flask
+      tags: ${DRONE_COMMIT_BRANCH}

Dockerfile

@@ -0,0 +1,48 @@
+FROM python:3.8-alpine as build
+
+RUN apk add --no-cache \
+    build-base \
+    gcc \
+    gettext \
+    git \
+    jpeg-dev \
+    libffi-dev \
+    libjpeg \
+    musl-dev \
+    postgresql-dev \
+    python3-dev \
+    zlib-dev
+
+RUN mkdir -p /app/{code,venv}
+WORKDIR /app/code
+COPY Pipfile Pipfile.lock /app/code/
+
+RUN python3 -m venv /app/venv
+RUN pip install pipenv setuptools
+ENV PATH="/app/venv/bin:$PATH" VIRTUAL_ENV="/app/venv"
+RUN pip install wheel cppy
+# Install dependencies into the virtual environment with Pipenv
+RUN pipenv install --deploy --verbose
+
+FROM python:3.8-alpine
+
+RUN apk add --no-cache \
+    cloud-utils \
+    libjpeg \
+    libpq \
+    libstdc++ \
+    libvirt-client \
+    openssh-client \
+    virt-install
+
+COPY . /app/code/
+WORKDIR /app/code
+
+COPY --from=build /app/venv /app/venv
+ENV PATH="/app/venv/bin:$PATH" VIRTUAL_ENV="/app/venv"
+
+CMD ["gunicorn", "--bind", "0.0.0.0:5000", "-k", "gevent", "--worker-connections", "1000", "app:app"]
+
+VOLUME /app/code
+
+EXPOSE 5000

capsulflask/__init__.py

@@ -27,11 +27,29 @@ class StdoutMockFlaskMail:
     def send(self, message: Message):
       current_app.logger.info(f"Email would have been sent if configured:\n\nto: {','.join(message.recipients)}\nsubject: {message.subject}\nbody:\n\n{message.body}\n\n")
 
+
 load_dotenv(find_dotenv())
 
+for var_name in [
+  "SPOKE_HOST_TOKEN", "HUB_TOKEN", "STRIPE_SECRET_KEY",
+  "BTCPAY_PRIVATE_KEY", "MAIL_PASSWORD"
+]:
+  var = os.environ.get(f"{var_name}_FILE")
+  if not var:
+    continue
+
+  if not os.path.isfile(var):
+    continue
+
+  with open(var) as secret_file:
+    os.environ[var_name] = secret_file.read().rstrip('\n')
+  del os.environ[f"{var_name}_FILE"]
+
 app = Flask(__name__)
 
 app.config.from_mapping(
+  FLASK_DEBUG=os.environ.get("FLASK_DEBUG", default="0"),
+
   BASE_URL=os.environ.get("BASE_URL", default="http://localhost:5000"),
   SECRET_KEY=os.environ.get("SECRET_KEY", default="dev"),
   HUB_MODE_ENABLED=os.environ.get("HUB_MODE_ENABLED", default="True").lower() in ['true', '1', 't', 'y', 'yes'],

docker-compose.yml

@@ -0,0 +1,36 @@
+---
+version: "3.8"
+
+services:
+  app:
+    image: 3wordchant/capsul-flask:latest
+    build: .
+    volumes:
+      - "./:/app/code"
+      - "../tank:/tank"
+      # - "/var/run/libvirt/libvirt-sock:/var/run/libvirt/libvirt-sock"
+    depends_on:
+      - db
+    ports:
+      - "5000:5000"
+    environment:
+      - "POSTGRES_CONNECTION_PARAMETERS=host=db port=5432 user=capsul password=capsul dbname=capsul"
+      - SPOKE_MODEL=shell-scripts
+        #- FLASK_DEBUG=1
+      - BASE_URL=http://localhost:5000
+      - ADMIN_PANEL_ALLOW_EMAIL_ADDRESSES=3wc.capsul@doesthisthing.work
+      - VIRSH_DEFAULT_CONNECT_URI=qemu:///system
+    # The image uses gunicorn by default, let's override it with Flask's
+    # built-in development server
+    command: ["flask", "run", "-h", "0.0.0.0", "-p", "5000"]
+  db:
+    image: "postgres:9.6.5-alpine"
+    volumes:
+      - "postgres:/var/lib/postgresql/data"
+    environment:
+      POSTGRES_USER: capsul
+      POSTGRES_PASSWORD: capsul
+      POSTGRES_DB: capsul
+
+volumes:
+  postgres: