Add more informative string repr of SQL type

Author: plamut

google/cloud/bigquery/standard_sql.py

@@ -168,6 +168,10 @@ def __eq__(self, other):
 
     __hash__ = None
 
+    def __str__(self):
+        result = f"{self.__class__.__name__}(type_kind={self.type_kind!r}, ...)"
+        return result
+
 
 class StandardSqlField:
     """A field or a column.

tests/unit/test_standard_sql_types.py

@@ -275,6 +275,11 @@ def test_from_api_repr_struct_type_incomplete_field_info(self):
         )
         assert result == expected
 
+    def test_str(self):
+        instance = self._make_one(type_kind=bigquery.StandardSqlTypeNames.BOOL)
+        bool_type_repr = repr(bigquery.StandardSqlTypeNames.BOOL)
+        assert str(instance) == f"StandardSqlDataType(type_kind={bool_type_repr}, ...)"
+
 
 class TestStandardSqlTableType:
     @staticmethod