feat: create volume for private LMS/CMS media assets (#1124)

Content Libraries will store asset files like images, transcripts, and
PDFs using Learning Core–which in turn uses django-storages and expects
some backing file store. These files should NOT be directly accessible
via the browser, both because of access policies and the fact that the
filenames will not be meaningful by themselves and must be translated by
app logic. For details see:

* https://github.com/openedx/openedx-learning/blob/main/docs/decisions/0015-serving-static-assets.rst
* https://github.com/openedx/openedx-learning/blob/main/openedx_learning/apps/authoring/contents/models.py
* https://github.com/openedx/openedx-learning/blob/main/openedx_learning/apps/authoring/components/models.py

The existing /data/openedx-media -> /openedx/media mount is publicly
accessible by browser, and so is not appropriate for this purpose. This
commit creates a parallel /data/openedx-media-private ->
/openedx/media-private volume mapping instead.

This commit also creates configuration needed for openedx-learning to
point to this new directory.

This commit does NOT currently add support for this in k8s, as that will
require changes to the minio plugin.

changelog.d/20240926_151223_dave_private_media.md

@@ -0,0 +1 @@
+- [Feature] Create a new /data/openedx-media-private volume to store media files that are not publicly accessible via the browser, and create configuration that Learning Core (openedx-learning) will use to access this storage space. Learning Core will use a sub-directory of /data/openedx-media-private to store Content Library file uploads, but other apps can create their own sub-directories for their own use. (by @ormsbee)

tutor/templates/apps/openedx/settings/partials/common_all.py

@@ -246,5 +246,14 @@
     "user": None,
 }
 
+OPENEDX_LEARNING = {
+    'MEDIA': {
+        "BACKEND": "django.core.files.storage.FileSystemStorage",
+        "OPTIONS": {
+            "location": "/openedx/media-private/openedx-learning",
+        }
+    }
+}
+
 {{ patch("openedx-common-settings") }}
 ######## End of settings common to LMS and CMS

tutor/templates/local/docker-compose.yml

@@ -15,6 +15,7 @@ services:
       - ../../data/lms:/mounts/lms
       - ../../data/cms:/mounts/cms
       - ../../data/openedx-media:/mounts/openedx
+      - ../../data/openedx-media-private:/mounts/openedx-private
       {% if RUN_MONGODB %}- ../../data/mongodb:/mounts/mongodb{% endif %}
       {% if RUN_MYSQL %}- ../../data/mysql:/mounts/mysql{% endif %}
       {% if RUN_ELASTICSEARCH %}- ../../data/elasticsearch:/mounts/elasticsearch{% endif %}
@@ -112,6 +113,7 @@ services:
       - ../apps/openedx/uwsgi.ini:/openedx/uwsgi.ini:ro
       - ../../data/lms:/openedx/data
       - ../../data/openedx-media:/openedx/media
+      - ../../data/openedx-media-private:/openedx/media-private
       {%- for mount in iter_mounts(MOUNTS, "openedx", "lms") %}
       - {{ mount }}
       {%- endfor %}
@@ -138,6 +140,7 @@ services:
       - ../apps/openedx/uwsgi.ini:/openedx/uwsgi.ini:ro
       - ../../data/cms:/openedx/data
       - ../../data/openedx-media:/openedx/media
+      - ../../data/openedx-media-private:/openedx/media-private
       {%- for mount in iter_mounts(MOUNTS, "openedx", "cms") %}
       - {{ mount }}
       {%- endfor %}
@@ -166,6 +169,7 @@ services:
       - ../apps/openedx/config:/openedx/config:ro
       - ../../data/lms:/openedx/data
       - ../../data/openedx-media:/openedx/media
+      - ../../data/openedx-media-private:/openedx/media-private
       {%- for mount in iter_mounts(MOUNTS, "openedx", "lms-worker") %}
       - {{ mount }}
       {%- endfor %}
@@ -185,6 +189,7 @@ services:
       - ../apps/openedx/config:/openedx/config:ro
       - ../../data/cms:/openedx/data
       - ../../data/openedx-media:/openedx/media
+      - ../../data/openedx-media-private:/openedx/media-private
       {%- for mount in iter_mounts(MOUNTS, "openedx", "cms-worker") %}
       - {{ mount }}
       {%- endfor %}