Add search and search_auto_paging_iter abstract methods (#873)

Author: yejia-stripe

stripe/api_resources/abstract/searchable_api_resource.py

@@ -21,3 +21,11 @@ def _search(
             stripe_account=stripe_account,
             params=params,
         )
+
+    @classmethod
+    def search(cls, *args, **kwargs):
+        raise NotImplementedError
+
+    @classmethod
+    def search_auto_paging_iter(cls, *args, **kwargs):
+        raise NotImplementedError