Convenience Client class generation

[timkendall]

In-order-to help with ease of use, we could generate a thin Client class wrapper around our query, mutation, and subscription primitives. It would expose methods for each top-level operation (as well-as expose more flexible query and mutation methods).

Example (with Starwars schema):

import { Transport, Operation } from '@timkendall/tql'

export class Starwars {
  constructor(private readonly transport: Transport) {}
  
  public viewer(select: ViewerSelector) {}

  public addReview(variables: AddReviewInput, select: AddReviewSelector ) {}

  public query(name: string, select: QuerySelector) {}

  public mutate(name: string, select: MutationSelector) {}

  private execute<T>(operation: Operation<T>) {
    //  execute GraphQL operation against `this.transport`
  }
}