Enable authentication

[Decipher]

Is your feature request related to a problem? Please describe.
As a user I want to see a demo with working authentication.

Describe the solution you'd like

• Updated Druxt to 0.18.0
• Update auth configuration
• Implement solution in backend for callback

Describe alternatives you've considered

• Create DruxtAuth module

Additional context
Config: authorization_code grant with PKCE support.

  auth: {
    redirect: {
      callback: '/callback',
      logout: '/',
    },
    strategies: {
      drupal: {
        scheme: 'oauth2',
        endpoints: {
          authorization: baseUrl + '/oauth/authorize',
          token: baseUrl + '/oauth/token',
          userInfo: baseUrl + '/oauth/userinfo',
        },
        clientId: process.env.OAUTH_CLIENT_ID,
        responseType: 'code',
        grantType: 'authorization_code',
        codeChallengeMethod: 'S256',
      },
    },
  },