Introduce GraphQL Importer

[ostridm]

The project currently lacks of an ability to import a GraphQL schema from an existing introspection response (e.g. IntrospectionQuery) or single human-readable schema or even a collection of such schemas.

Proposed solution:

Since the GraphQL is not supposed to carry the URL information, we declare special envelope wrapping both an IntrospectionQuery or schema and URL.

To achieve this, the @har/sdk-core package utilized. Also, to be aligned with other API types re-exported from @har/sdk-core the graphql package types also are to be re-exported as follows:

export * from 'graphql';
import { IntrospectionQuery } from 'graphql';

export namespace GraphQL {
  export interface GraphQLEnvelope<
    T extends IntrospectionQuery | string | string[]
  > {
    url: string;
    data: T;
  }
}

We are introducing GraphQL.Document convenience type for further usage.

export namespace GraphQL {
  export type Document = GraphQLEnvelope<IntrospectionQuery>;
}

Extend ImporterType enumeration

export enum ImporterType {
  GRAPHQL = 'graphql'
}

Extend Doc conditional type deriving from ImporterType.GRAPHQL and GraphQL.Document

export type Doc<T extends DocType> = 
...
  : T extends ImporterType.GRAPHQL
  ? GraphQL.Document
...

Introduce a new Importer implementation

export class GraphQLImporter extends BaseImporter<ImporterType.GRAPHQL, GraphQL.Document> 

Expected results:

GraphQLImporter able to handle GraphQL.Doument import as follows:

Given an IntrospectionQuery envelope

const document: GraphQL.Document  = {
  "url": "https://example.com/graphql",
  "data": {
    "__schema": {
      "description": null,
      "queryType": {
        "name": "Query"
      },
      "mutationType": null,
      "subscriptionType": null,
      types:  [...],
      directives:  [...],
    }
  }
};

const importer = new GraphQLImporter();

const imported = await  importer.import(JSON.stringify(document));

Expect the imported contains the equivalent of document

Given a single SDL schema

const document: GraphQL.GraphQLEnvelope<string>  = {
          url: 'https://example.com/graphql',
          data: 'type Foo { bar : String!} type Query { foo: Foo }'
        };

const importer = new GraphQLImporter();

const imported = await  importer.import(JSON.stringify(document));

Expect the imported contains the converted introspection which is an equivalent of schema given

Given a collection of SDL schema

const document: GraphQL.GraphQLEnvelope<string[]>  = {
          url: 'https://example.com/graphql',
         data: ['type Foo { bar : String!}', 'type Query { foo: Foo }']
        };

const importer = new GraphQLImporter();

const imported = await  importer.import(JSON.stringify(document));

Expect the imported contains the converted introspection which is an equivalent of joined schema given