Followup on #13

Prepare SSO Drupal instance

[x] Setup new Docker containers for SSO;
[x] Setup initial SSO Drupal installation;
[x] Install simple_oauth module;
[x] Generate certificates for simple_oauth using omgwtfssl docker container;
[x] Configure simple_oauth global settings;
[x] Add new Drupal instance to Falcon codebase;
[x] Create new simple_oauth client config entity;
[x] Test auth token generation according to simple_oauth docs.
[x] Create simple_oauth_sso module to support SSO features.
[x] Implement auth route and a controller.
[x] Implement login form which will authenticate user against simple_oauth;
[x] Implement login.js custom library which will handle login form;
[x] Implement redirect after authentication;
[ ] Write documentation on using simple_oauth_sso with simple_oauth.
[ ] Configure SSO instance for platform.sh;

Implement Drupal 8 sso_client module for backend services

[ ] Implement custom AuthenticationProvider;
[ ] Receive auth token from API Bus;
[ ] Make request to SSO and try to authenticate using auth token;
[ ] Create "proxy" user if it's new;
[ ] Store session for the user with same expiration and validation details provided from SSO.
[ ] If received request with already authenticated valid token and session is not expired yet, authenticate user;

[ ] Implement a login button which will take user to SSO auth route with proper redirect back url in query parameter.
[ ] Implement a login handler for when user gets back with auth token in query parameter;
[ ] Store auth token, refresh token and expire date in local storage.
[ ] Implement auth client which will send auth token to API Bus and gets authenticated user data as a response;
[ ] Store user data in local storage;
[ ] Implement token validation handler, so if it's not valid or expired, user should be redirected to SSO auth route;

[ ] get to know to API Bus and implement proper way to handle and pass requests from frontend to backend services;