feat: add status_code property on http error handling (#1185)

Fixes #1183 🦕
Fixes #1255 🦕
- Add status code property in http error handler class.
- Resolve issue where error_details is not populated.
diff --git a/tests/test_errors.py b/tests/test_errors.py
index 78dee17..9c139a6 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -83,6 +83,8 @@
             reason="Failed",
         )
         error = HttpError(resp, content, uri="http://example.org")
+        self.assertEqual(error.error_details, "error details")
+        self.assertEqual(error.status_code, 400)
         self.assertEqual(
             str(error),
             '<HttpError 400 when requesting http://example.org returned "country is required". Details: "error details">',