fix: set pool_pre_ping to true (#9)

https://stackoverflow.com/questions/55457069/how-to-fix-operationalerror-psycopg2-operationalerror-server-closed-the-conn

Closes #8

settings.py

@@ -7,6 +7,8 @@ class Config(object):
     PROJECT_ROOT = os.path.abspath(os.path.dirname(__file__))
     SQLALCHEMY_TRACK_MODIFICATIONS = False
     SWAGGER_UI_DOC_EXPANSION = "list"
+    # pool_pre_ping should help handle DB connection drops
+    SQLALCHEMY_ENGINE_OPTIONS = {"pool_pre_ping": True}
 
 
 class ProductionConfig(Config):