Implement dataloader

[preetjdp]

What Does this PR do?.

Adds Dataloader to the server to batch and cache User queries.

Describe In brief the solution / approach you've gone with.

The approach used here uses Dataloader of which a new instance is created on every new connection.

The Dataloader is then made available using dependency injection mentioned here.
MichalLytek/type-graphql#51 (comment)

Describe alternatives you may have considered

• A alternate would have been to add Dataloader to the appContext, but the problem with that is would have been difficult to manage and expand overtime.

• Use the dataloader over larger time, use it more as a cache with a different lifecycle than that of the request.
  Pros of this approach.
  This would mean significantly lesser hits to the database and that's amazing.

** Cons of this approach**
Would be difficult to maintain the lifecycle of the Dataloader and may lead to significant memory leaks and hell.

Additional context / quirks

Add any other context, screenshots, or quirks about the implmentation here.