Add support for LMS_INTERNAL_ROOT_URL.

This adds ability to configure the LMS_INTERNAL_ROOT_URL setting via the
EDXAPP_LMS_INTERNAL_ROOT_URL ansible variable. The value of the new
variable is used instead of EDXAPP_LMS_ROOT_URL to construct enterprise
API URLs, which are used for internal communication. In some deployment
scenarios, it is not desirable for internal communication to be carried
out via the external URLs.

This change is backwards compatible since the new EDXAPP_LMS_INTERNAL_ROOT_URL
defaults to the value of EDXAPP_LMS_ROOT_URL.

CHANGELOG.md

 - Role: edxapp
+  - Added `EDXAPP_LMS_INTERNAL_ROOT_URL` setting (defaults to `EDXAPP_LMS_ROOT_URL`).
+
+- Role: edxapp
   - Added `EDXAPP_CELERY_BROKER_TRANSPORT` and renamed `EDXAPP_RABBIT_HOSTNAME`
     to `EDXAPP_CELERY_BROKER_HOSTNAME`. This is to support non-amqp brokers,
     specifically redis. If `EDXAPP_CELERY_BROKER_HOSTNAME` is unset it will use

playbooks/roles/edxapp/defaults/main.yml

@@ -336,6 +336,7 @@ EDXAPP_BULK_EMAIL_LOG_SENT_EMAILS: false
 EDXAPP_UNIVERSITY_EMAIL: 'university@example.com'
 EDXAPP_PRESS_EMAIL: 'press@example.com'
 EDXAPP_LMS_ROOT_URL: "{{ EDXAPP_LMS_BASE_SCHEME | default('https') }}://{{ EDXAPP_LMS_BASE }}"
+EDXAPP_LMS_INTERNAL_ROOT_URL: "{{ EDXAPP_LMS_ROOT_URL }}"
 EDXAPP_LMS_ISSUER: "{{ COMMON_JWT_ISSUER }}"
 EDXAPP_JWT_EXPIRATION: 30  # Number of seconds until expiration
 EDXAPP_JWT_AUDIENCE: "{{ COMMON_JWT_AUDIENCE }}"
@@ -738,7 +739,7 @@ EDXAPP_BLOCK_STRUCTURES_SETTINGS:
   TASK_MAX_RETRIES: 5
 
 # Configuration settings needed for the LMS to communicate with the Enterprise service.
-EDXAPP_ENTERPRISE_API_URL: "{{ EDXAPP_LMS_ROOT_URL }}/enterprise/api/v1"
+EDXAPP_ENTERPRISE_API_URL: "{{ EDXAPP_LMS_INTERNAL_ROOT_URL }}/enterprise/api/v1"
 
 EDXAPP_ENTERPRISE_SERVICE_WORKER_EMAIL: "enterprise_worker@example.com"
 EDXAPP_ENTERPRISE_SERVICE_WORKER_USERNAME: "enterprise_worker"
@@ -747,7 +748,7 @@ EDXAPP_ENTERPRISE_COURSE_ENROLLMENT_AUDIT_MODES:
   - audit
   - honor
 
-EDXAPP_ENTERPRISE_ENROLLMENT_API_URL: "{{ EDXAPP_LMS_ROOT_URL }}/api/enrollment/v1/"
+EDXAPP_ENTERPRISE_ENROLLMENT_API_URL: "{{ EDXAPP_LMS_INTERNAL_ROOT_URL }}/api/enrollment/v1/"
 
 # The default value of this needs to be a 16 character string
 EDXAPP_ENTERPRISE_REPORTING_SECRET: '0000000000000000'
@@ -1015,6 +1016,7 @@ generic_env_config:  &edxapp_generic_env
   LMS_BASE: "{{ EDXAPP_LMS_BASE }}"
   CMS_BASE: "{{ EDXAPP_CMS_BASE }}"
   LMS_ROOT_URL: "{{ EDXAPP_LMS_ROOT_URL }}"
+  LMS_INTERNAL_ROOT_URL: "{{ EDXAPP_LMS_INTERNAL_ROOT_URL }}"
   PARTNER_SUPPORT_EMAIL: "{{ EDXAPP_PARTNER_SUPPORT_EMAIL }}"
   PLATFORM_NAME: "{{ EDXAPP_PLATFORM_NAME }}"
   PLATFORM_DESCRIPTION: "{{ EDXAPP_PLATFORM_DESCRIPTION }}"