implement secret_key config

.env.prod-sample

@@ -1,6 +1,7 @@
 FLASK_ENV=production
 FLASK_APP=forest/__init__.py
 APP_FOLDER=/home/app/web
+SECRET_KEY=1dff602d522785d27d5bc203
 
 SQL_HOST=db
 SQL_PORT=5432

flask/forest/config.py

@@ -5,6 +5,7 @@ basedir = os.path.abspath(os.path.dirname(__file__))
 
 
 class Config(object):
+    SECRET_KEY = f"{os.getenv('SECRET_KEY')}"
     SQLALCHEMY_DATABASE_URI = os.getenv("DATABASE_URL", "sqlite://")
     SQLALCHEMY_TRACK_MODIFICATIONS = False
     STATIC_FOLDER = f"{os.getenv('APP_FOLDER')}/forest/static"