init app of test arena

asf-cloud-server/testarena/backend/app/database.py

@@ -0,0 +1,11 @@
+from sqlalchemy import create_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+import os
+
+SQLALCHEMY_DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://user:password@db/testarena")
+
+engine = create_engine(SQLALCHEMY_DATABASE_URL)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+Base = declarative_base()