add default configuration for neo4j

playbooks/roles/edxapp/defaults/main.yml

@@ -187,6 +187,16 @@ EDXAPP_ENABLE_READING_FROM_MULTIPLE_HISTORY_TABLES: True
 EDXAPP_GIT_REPO_DIR: '/edx/var/edxapp/course_repos'
 EDXAPP_GIT_REPO_EXPORT_DIR: '/edx/var/edxapp/export_course_repos'
 
+EDXAPP_NEO4J_CONFIG: !!null
+  # Setting this to null as a default. Here's what an example configuration
+  # would look like:
+  # bolt: True
+  # password: 'password'
+  # user: 'neo4j'
+  # https_port: 7473
+  # host: 'localhost'
+  # secure: True
+
 EDXAPP_ONLOAD_BEACON_SAMPLE_RATE: 0.0
 
 EDXAPP_FINANCIAL_REPORTS:
@@ -973,6 +983,7 @@ lms_auth_config:
                 render_template: 'edxmako.shortcuts.render_to_string'
   PROCTORING_BACKEND_PROVIDER: "{{ EDXAPP_PROCTORING_BACKEND_PROVIDER }}"
   SOCIAL_AUTH_OAUTH_SECRETS: "{{ EDXAPP_SOCIAL_AUTH_OAUTH_SECRETS }}"
+  NEO4J_CONFIG: "{{ EDXAPP_NEO4J_CONFIG }}"
 
 
 lms_env_config: