Enable settings injection via Docker env

Dockerfile

@@ -10,4 +10,7 @@ COPY . /doccano
 
 WORKDIR /doccano
 
+ENV DEBUG="True"
+ENV SECRET_KEY="change-me-in-production"
+
 CMD ["/venv/bin/gunicorn", "--bind=0.0.0.0:80", "--workers=2", "--pythonpath=app", "app.wsgi"]

app/app/settings.py

@@ -23,7 +23,9 @@ BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 # See https://docs.djangoproject.com/en/2.0/howto/deployment/checklist/
 
 # SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = 'v8sk33sy82!uw3ty=!jjv5vp7=s2phrzw(m(hrn^f7e_#1h2al'
+SECRET_KEY = os.environ.get(
+    'SECRET_KEY',
+    'v8sk33sy82!uw3ty=!jjv5vp7=s2phrzw(m(hrn^f7e_#1h2al')
 
 # SECURITY WARNING: don't run with debug turned on in production!
 DEBUG = True