Update documentation for DB strategy and fix DB dependencies versions

docs/src/db_sqlalchemy_access_tokens.py

@@ -0,0 +1,39 @@
+import databases
+import sqlalchemy
+from fastapi_users.db import SQLAlchemyBaseUserTable, SQLAlchemyUserDatabase
+from fastapi_users_db_sqlalchemy.access_token import (
+    SQLAlchemyAccessTokenDatabase,
+    SQLAlchemyBaseAccessTokenTable,
+)
+from sqlalchemy.ext.declarative import DeclarativeMeta, declarative_base
+
+from .models import AccessToken, UserDB
+
+DATABASE_URL = "sqlite:///./test.db"
+database = databases.Database(DATABASE_URL)
+Base: DeclarativeMeta = declarative_base()
+
+
+class UserTable(Base, SQLAlchemyBaseUserTable):
+    pass
+
+
+class AccessTokenTable(SQLAlchemyBaseAccessTokenTable, Base):
+    pass
+
+
+engine = sqlalchemy.create_engine(
+    DATABASE_URL, connect_args={"check_same_thread": False}
+)
+Base.metadata.create_all(engine)
+
+users = UserTable.__table__
+access_tokens = AccessTokenTable.__table__
+
+
+async def get_user_db():
+    yield SQLAlchemyUserDatabase(UserDB, database, users)
+
+
+async def get_access_token_db():
+    yield SQLAlchemyAccessTokenDatabase(AccessToken, database, access_tokens)