ENT-854 Adding FERNET_KEYS setting.

CHANGELOG.md

 - Role: edxapp
+  - Added `EDXAPP_FERNET_KEYS` to allow for use of django-fernet-keys in LMS.
+  
+- Role: edxapp
   - Added `EDX_PLATFORM_REVISION` (set from `edx_platform_version`). This is for
   edx-platform debugging purposes, and replaces calling dealer.git at startup.
 

playbooks/roles/edxapp/defaults/main.yml

@@ -146,6 +146,9 @@ EDXAPP_COMMENTS_SERVICE_KEY:  'password'
 
 EDXAPP_EDXAPP_SECRET_KEY: "DUMMY KEY CHANGE BEFORE GOING TO PRODUCTION"
 
+EDXAPP_FERNET_KEYS:
+  - "DUMMY KEY CHANGE BEFORE GOING TO PRODUCTION"
+
 EDXAPP_LTI_USER_EMAIL_DOMAIN: "lti.example.com"
 # 900s, or 15 mins
 EDXAPP_LTI_AGGREGATE_SCORE_PASSBACK_DELAY: 900
@@ -1252,6 +1255,7 @@ lms_auth_config:
   ACE_CHANNEL_SAILTHRU_API_SECRET: "{{ EDXAPP_ACE_CHANNEL_SAILTHRU_API_SECRET }}"
   ENTERPRISE_REPORTING_SECRET: "{{ EDXAPP_ENTERPRISE_REPORTING_SECRET }}"
   ANALYTICS_API_KEY: "{{ EDXAPP_LMS_ANALYTICS_API_KEY }}"
+  FERNET_KEYS: "{{ EDXAPP_FERNET_KEYS }}"
 
 
 lms_env_config: