[ADD]document_url_google_drive: attach document from Google Drive

document_url_google_drive/readme/CONFIGURE.md

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+To configure this module, you need to:
+
+- Go to Settings -> General Settings and scroll down to the Integrations section.
+
+- Enable "Google API", save. Setup instructions https://developers.google.com/drive/picker/guides/overview
+
+  - "Google Client ID" - enter the client ID from the Google API console: https://developers.google.com/identity/oauth2/web/guides/get-google-api-clientid
+  - "Google API key" - enter the API key from the Google API console.
+  - "Google App ID" - enter the ID of the Google application. The default value is
+    `odoo`.
+
+You will be asked to authenticate when you add a link for the first time.
+
+![Configuration](../static/img/google_api_settings.png)
+
+**To modify your personal login credentials later**
+
+- Open your user profile and set up personal access credentials on the "Google
+  API" tab.
+
+  - field "Google Scope" - enter the scope for the Google API. The default value is
+    `https://www.googleapis.com/auth/drive.readonly`.
+  - field "Google Access Token" - your token will be displayed here. It is necessary to
+    edit it.
+  - field "Google Mime Types" - enter the file formats to be filtered when selecting.
+    Example: `application/pdf, image/jpeg, image/png`. By default, all files are
+    selected
+
+  You can always log off from the current Google Account by clicking the "logout" icon right to the "Add GDrive link".
+
+

document_url_google_drive/readme/CONTRIBUTORS.md

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+ Cetmix <cetmix.com>
+    Ivan Sokolov
+    Mykola Demchuk

document_url_google_drive/readme/DESCRIPTION.md

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+This module extends the functionality of the document_url module and allows you to
+attach a link to a file from your Google Drive

document_url_google_drive/readme/USAGE.md

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+To use this module, you need to:
+
+1. Open the form view of an object (Example: Customer Invoice INV/2019/0007).
+1. Go to the chatter and click on the attached icon.
+1. Click **Add GDrive link**.
+1. Fill the wizard fields and click on Add button.
+1. In the open window, select the files you need and press the select button.
+1. You will see a new **URL attachment** in the set of attachments related to the object.
+1. In order to log in under another google user, click on the logout icon located after **Add GDrive link**
+
+![Google Drive Link](../static/img/gdrive_link.png)