login.js

import Controller from '@ember/controller';
import { inject as service } from '@ember/service';
import { action } from "@ember/object";
import { tracked } from "@glimmer/tracking";

export default class LoginController extends Controller {
  @tracked errorMessage;
  @service session;

  identification = '[email protected]';
  password = 'password';

  @action
  authenticate() {
    let { identification, password } = this;
    return this.session.authenticate(
      'authenticator:my', identification, password
    )
    .then(() => {
      this.transitionTo('index');
    })
    .catch(e => {
      if (e.errors) {
        log(`Error: ${e.errors[0].title}`);
        return this.set('errorMessage', e.errors[0]);
      }
      return reject(e);
    });
  }
}

my-authenticator.js

import DeviseAuthenticator from 'ember-simple-auth/authenticators/devise';
import ENV from 'id/config/environment';
import { isEmpty } from '@ember/utils';
import { merge, assign as emberAssign } from '@ember/polyfills';
import fetch from 'fetch';

const assign = emberAssign || merge;

export default class MyAuthenticator extends DeviseAuthenticator {

  serverTokenEndpoint = `${ENV.APP.hosts.api}/user_authentications/`;
  resourceName = 'attributes';
  tokenAttributeName = 'jwt';

  // authenticate(identification, password) {
  //   return new Promise((resolve, reject) => {
  //     const { resourceName, identificationAttributeName, tokenAttributeName } = this.getProperties('resourceName', 'identificationAttributeName', 'tokenAttributeName');
  //     const data = {};
  //     data[resourceName] = { password };
  //     data[resourceName][identificationAttributeName] = identification;
  //
  //     this.makeRequest(data).then((response) => {
  //       console.log('hi');
  //       if (response.ok) {
  //         response.json().then((json) => {
  //           if (this._validate(json)) {
  //             run(null, resolve, json);
  //           } else {
  //             run(null, reject, `Check that server response includes ${tokenAttributeName} and ${identificationAttributeName}`);
  //           }
  //         });
  //       } else {
  //         run(null, reject, response);
  //       }
  //     }).catch((error) => run(null, reject, error));
  //   });
  // }

  makeRequest(data, options = {}) {
    let url = options.url || this.get('serverTokenEndpoint');
    let requestOptions = {};
    let body = JSON.stringify(
      { data: { type: "user_authentications", attributes: data['attributes'] } }
    );
    assign(requestOptions, {
      body,
      method: 'POST',
      headers:  {
        'Accept': ENV.APP.jsonContentType,
        'Content-Type': ENV.APP.jsonContentType
      }
    });
    assign(requestOptions, options || {});
    return fetch(url, requestOptions);
  }

  _validate(data) {
    const _data = data['data']['attributes'] ? data['data']['attributes'] : data;
    return !isEmpty(_data['jwt']) && !isEmpty(_data['user_id']);
  }

}