Inconsistent created dates on groups and projects imported with direct transfer

Problem

In direct transfer, groups' created dates are set to the time they were imported, while projects' created dates preserve the original created date on the source. It's particularly noticeable when importing groups with projects because the parent groups look notably newer than their descendant projects:

Proposed solution

Make groups imported by direct transfer preserve their created date on the source.

Proposed implementation

Update GetGroupQuery to include createdAt and update GroupAttributesTransformer to include created_at in the transformed params hash.