message: types: map relationships to ModelInstance
diff: +import DS from 'ember-data';
  import { Document } from 'osf-api';
  export { default as faker } from 'faker';
  @@ -140,6 +141,11 @@ function handlerDefinition(
  export type resourceAction = 'index' | 'show' | 'create' | 'update' | 'delete';
  +export type ModelAttrs<T> = {
  + [P in keyof T]: T[P] extends DS.Model & DS.PromiseObject<infer M> ? ModelInstance<M> :
  + T[P] extends DS.Model ? ModelInstance<T[P]> : T[P];
  +};
  +
  export interface Server {
  schema: Schema;
  db: Database;
  @@ -173,7 +179,7 @@ export interface Server {
  ): ModelInstance<T>;
  create<T extends AnyAttrs = AnyAttrs>(
  modelName: string,
  - attrs?: Partial<T>,
  + attrs?: Partial<ModelAttrs<T>>,
  ...traits: string[]
  ): ModelInstance<T>;
  @@ -185,7 +191,7 @@ export interface Server {
  createList<T extends AnyAttrs = AnyAttrs>(
  modelName: string,
  amount: number,
  - attrs?: Partial<T>,
  + attrs?: Partial<ModelAttrs<T>>,
  ...traits: string[]
  ): Array<ModelInstance<T>>;
  