Reduce the generated code in file query_root.rs

[karatakis]

Motivation

Migrating a SeaORM project into GraphQL can be greatly improved by using the functions provided in the Seaography library.
The problem is that it requires information in the form of code to be passed to the library in order to generate the GraphQL schema, and this information is tedious to be written by hand. In order to solve that Seaography comes with a CLI tool that generates the file, but in case someone wants to configure it manually the generated file requires lots of information. In this issue we will make query_root.rs file to contains only the information it requires.

Proposed Solutions

Use information that SeaORM provide and hide implementation detains from query_root.rs file.