feat: Avoid joins when only fetching an ID

[mselee]

Description

Consider the following query

query Query {
  books {
    id
    author {
      id
    }
  }
}

A join will be generated even though we really don't have to, as the required information already exists through book.author_id. The idea here is to try and optimize away this join, by constructing the Author object in-memory using the value from book.author_id.

I'm not very familiar with the code base, so I'm not sure if this is has other drawbacks.

Types of Changes

• [ ] Core
• [ ] Bugfix
• [ ] New feature
• [x] Enhancement/optimization
• [ ] Documentation

Checklist

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[Sanyambansal76]

@mselee want to check if you are waiting for help to update the PR?