require client-key for uploads

Dockerfile

@@ -4,4 +4,10 @@ COPY ./src /app
 COPY requirements.txt /app/requirements.txt
 RUN pip install -r /app/requirements.txt
 EXPOSE 7777
+
+# The actual values should be provided when running the container
+ENV CLIENT_KEY=default-secret-key \
+    UPLOAD_FOLDER=tmp/uploads \
+    DEBUG=False
+
 CMD ["gunicorn", "wsgi:app", "--bind", "0.0.0.0:7777"]