Simplified Google Drive API access based on google/apiclient

• set up the Google client secret and download it as JSON file (see below id you need instructions for that)
• move it to the examples/config folder
• CLI version
  • rename it to app_secret_cli.json
  • open terminal, go to the examples/cli folder
    • run php index.php
    • open the URL
    • enter the verification code
    • now you should see a (partial) list of the content of your drive
    • run it again, now you should see the same list without the hassle of managing the verification code
• HTTP version
  • rename it to app_secret_http.json
  • set up a web server with examples/http as doc root
  • open http://< your (local) web server url >
    • given you have a local system gd-test.app set up:
      • http://gd-test.app/index.php

• go to https://console.developers.google.com
• create new or open existing project
• got to API Manager, enable Google Drive API
• go to Credentials and create new OAuth Client ID
• if it is the first time, you need to setup the consent screen
  • enter product name and an optional URL
• CLI version
  • In the list with application types, choose other and give it a name
• HTTP version
  • In the list with application types, choose Web Application and give it a name
  • In the field Authorized redirect URIs enter:
    • http://< your (local) web server url >/< OAuth2 callback handler >
      • to run the examples (given you have a local system gd-test.app set up):
      • http://gd-test.app/redirecttarget.php
• Confirm the popup with client id and secret -> you don't need to remember those now
• Instead, download the whole credentials as json from the list with all client IDs
• move the file to any destination you like an make sure you give the correct path to the service