♻️ Refactor types to properly support Pydantic 2.7 (#913)

sqlmodel/_compat.py

@@ -18,11 +18,13 @@ from typing import (
     Union,
 )
 
-from pydantic import VERSION as PYDANTIC_VERSION
+from pydantic import VERSION as P_VERSION
 from pydantic import BaseModel
 from pydantic.fields import FieldInfo
 from typing_extensions import get_args, get_origin
 
+# Reassign variable to make it reexported for mypy
+PYDANTIC_VERSION = P_VERSION
 IS_PYDANTIC_V2 = PYDANTIC_VERSION.startswith("2.")