* OAuth 2.0 Classes Added
Added oauthlib in requirement.txt
Added class WebApplicationServer for Authorization code grant and Bearer tokens.
Added class OAuthWebRequestValidator for Validating Oauth Request for Web Application
* copied code from mnt_oauth needs review
* [New] OAuth2 Doctypes and endpoints added
Integrations > OAuth Provider Settings
Integration Broker > OAuth Bearer Token
Integration Broker > OAuth Authorization Code
Integration Broker > OAuth Client
endpoints for authorize, approve, get_token, revoke_token and test_resource
* oauth2.py: renamed skipauth to skip_auth
* [Fix] Parse URL instead of storing it in settings
* [Fix] get skip_auth from OAuth Provider Settings
* Success URL format. Failure URL added. Confirmation dialog layout changed.
* Validate access token if passed during use of REST API
* OAuth Confirmation colours fixed
* Multiple Changes
Added links for OAuth under Integrations in Module list.
Updated permissions on OAuth doctypes.
Updated layout of OAuth Client doctype.
* [Docs] Integrations > How to setup OAuth
* [Docs] Integration > Using OAuth
* [Fix] get_token endpoint must to handle POST request
* [Fix] http verbs and responses for OAuth 2.0 Endpoints
* [Fix] accept oauth2 access_token from headers
* Removed unused imports from api.py
