Fix lazy loaded nested associations - #153

Closes #129

What is the current behavior?

Relationships blocks are empty when including nested lazy loaded relationships.

What is the new behavior?

Relationship blocks are properly populated when including nested lazy loaded relationships. The behavior is now consistent with the non-lazy behavior.

The root cause of the problem was that the includes_list passed to #record_hash was not correctly formatted, resulting in included always being false. The behavior of #record_hash is now consistent with #get_included_records.

Checklist

Please make sure the following requirements are complete:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes /
  features)
• All automated checks pass (CI/CD)