refractor structure project and add user endpoint

backend/app/core/database.py

@@ -0,0 +1,26 @@
+from datetime import datetime
+
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
+from sqlalchemy import MetaData, NullPool, func
+
+from app.core.config import settings
+from app.core.constants import DB_NAMING_CONVENTION
+
+
+class Base(DeclarativeBase):
+    metadata = MetaData(naming_convention=DB_NAMING_CONVENTION)
+    
+    created_at: Mapped[datetime] = mapped_column(server_default=func.now())
+    updated_at: Mapped[datetime] = mapped_column(server_default=func.now(), onupdate=func.now())
+
+
+if settings.MODE == "TEST":
+    DATABASE_URL = settings.TEST_DATABASE_URL
+    DATABASE_PARAMS = {"poolclass": NullPool}
+else:
+    DATABASE_URL = settings.DATABASE_URL
+    DATABASE_PARAMS = {}
+
+async_engine = create_async_engine(DATABASE_URL, **DATABASE_PARAMS)
+async_session_maker = async_sessionmaker(async_engine, expire_on_commit=False)