expose relationship links

[mpugach]

In some cases, there are too many relations and we need to paginate them.

Also, we would like to utilize nested routes (chats/1/messages instead of messages?filter[chat]=1).

Dunno is it related to #103

Can we just expose the relationship links? Because it feels natural to receive them from the backend.

Then we could do something like this:

export class DatastoreService extends JsonApiDatastore {
  constructor(http: HttpClient) {
    super(http);

    this.headers = new HttpHeaders({
      accept: 'application/vnd.api+json',
      'content-type': 'application/vnd.api+json',
      'x-auth-token': getSomeToken(),
    });
  }

  getRelationPageOrSomthingBetterNamed(
    model: ModelType<JsonApiModel>,
    url: string
  ) {
    return this.findAll(
        model,
        {},
        this.getOptions().headers,
        url
      );
  }
}

const messageObservable = this.datastore.getRelationPageOrSomthingBetterNamed(
  Message,
  chat.relationshipLinks.messages.links.next // http://localhost:7000/api/v1/chats/1/messages?page[number]=2
);

[coveralls]

Coverage increased (+0.1%) to 91.312% when pulling 198de23 on mpugach:expose_relationship_links into 378c4dd on ghidoz:master.

[mpugach]

closed due to lack of response