add v2 omit by default

fastapi/_compat/main.py

@@ -175,6 +175,8 @@ def serialize_sequence_value(*, field: ModelField, value: Any) -> Sequence[Any]:
 
     return v2.serialize_sequence_value(field=field, value=value)  # type: ignore[arg-type]
 
+def omit_by_default(field_info: FieldInfo) -> tuple[FieldInfo, dict[str, Any]]:
+    return v2.omit_by_default(field_info=field_info)  # type: ignore[arg-type]
 
 def get_compat_model_name_map(fields: list[ModelField]) -> ModelNameMap:
     v1_model_fields = [