DM-46034: Remove remaining declarative_base references

docs/user-guide/database/initialize.rst

@@ -19,14 +19,16 @@ In the file :file:`schema/base.py`, define the SQLAlchemy declarative base:
 
 .. code-block:: python
 
-   from sqlalchemy.orm import declarative_base
+   from sqlalchemy.orm import DeclarativeBase
+
 
-   Base = declarative_base()
+   class Base(DeclarativeBase):
+       """Declarative base for SQLAlchemy ORM model of database schema."""
 
-In other files in that directory, define the database tables using the normal SQLAlchemy ORM syntax, one table per file.
+In other files in that directory, define the database tables using the `normal SQLAlchemy ORM syntax <https://docs.sqlalchemy.org/en/20/orm/mapping_styles.html#declarative-mapping>`__, one table per file.
 Each database table definition must inherit from ``Base``, imported from ``.base``.
 
-In :file:`schema/__init__.py`, import the table definitions from all of the files in the directory, as well as the ``Base`` variable, and export them using ``__all__``.
+In :file:`schema/__init__.py`, import the table definitions from all of the files in the directory, as well as the ``Base`` class, and export them using ``__all__``.
 
 Using non-default PostgreSQL schemas
 ------------------------------------

safir/tests/dependencies/db_session_test.py

@@ -8,10 +8,10 @@
 import structlog
 from fastapi import Depends, FastAPI
 from httpx import ASGITransport, AsyncClient
-from sqlalchemy import Column, String
+from sqlalchemy import String
 from sqlalchemy.ext.asyncio import async_scoped_session
 from sqlalchemy.future import select
-from sqlalchemy.orm import declarative_base
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
 
 from safir.database import (
     create_async_session,
@@ -20,15 +20,17 @@
 )
 from safir.dependencies.db_session import db_session_dependency
 
-Base = declarative_base()
+
+class Base(DeclarativeBase):
+    """Declarative base for testing."""
 
 
 class User(Base):
     """Tiny database table for testing."""
 
     __tablename__ = "user"
 
-    username: str = Column(String(64), primary_key=True)
+    username: Mapped[str] = mapped_column(String(64), primary_key=True)
 
 
 @pytest.mark.asyncio