Add oauth access token for zendesk integration

LEARNER-2736

CHANGELOG.md

@@ -447,3 +447,6 @@
 - Role: edxapp
   - Added `EDXAPP_VIDEO_TRANSCRIPTS_SETTINGS` to configure S3-backed video transcripts.
   - Removed unused `EDXAPP_BOOK_URL` setting
+
+- Role: edxapp
+  - Added `EDXAPP_ZENDESK_OAUTH_ACCESS_TOKEN` for making requests to Zendesk through front-end.

playbooks/roles/edxapp/defaults/main.yml

@@ -148,6 +148,7 @@ EDXAPP_ZENDESK_USER: ""
 EDXAPP_ZENDESK_URL: ""
 EDXAPP_ZENDESK_API_KEY: ""
 EDXAPP_ZENDESK_CUSTOM_FIELDS: {}
+EDXAPP_ZENDESK_OAUTH_ACCESS_TOKEN: ""
 EDXAPP_CELERY_USER: 'celery'
 EDXAPP_CELERY_PASSWORD: 'celery'
 EDXAPP_CELERY_BROKER_VHOST: ""
@@ -950,6 +951,7 @@ edxapp_generic_auth_config:  &edxapp_generic_auth
   YOUTUBE_API_KEY: "{{ EDXAPP_YOUTUBE_API_KEY }}"
   ZENDESK_USER: "{{ EDXAPP_ZENDESK_USER }}"
   ZENDESK_API_KEY: "{{ EDXAPP_ZENDESK_API_KEY }}"
+  EDXAPP_ZENDESK_OAUTH_ACCESS_TOKEN: "{{ EDXAPP_ZENDESK_OAUTH_ACCESS_TOKEN }}"
   CELERY_BROKER_USER: "{{ EDXAPP_CELERY_USER }}"
   CELERY_BROKER_PASSWORD: "{{ EDXAPP_CELERY_PASSWORD }}"
   GOOGLE_ANALYTICS_ACCOUNT: "{{ EDXAPP_GOOGLE_ANALYTICS_ACCOUNT }}"