fix: units added from libraries have block_type=unit

and so:

* contenstore helper is_unit needs to know about this new block type
* unit blocks don't have a "discussion_enabled" property
* upstream sync needs to use the container type string, not its olx_tag

Author: pomegranited

cms/djangoapps/contentstore/helpers.py

@@ -75,7 +75,7 @@ def is_unit(xblock, parent_xblock=None):
     Returns true if the specified xblock is a vertical that is treated as a unit.
     A unit is a vertical that is a direct child of a sequential (aka a subsection).
     """
-    if xblock.category == 'vertical':
+    if xblock.category == 'vertical' or xblock.category == 'unit':
         if parent_xblock is None:
             parent_xblock = get_parent_xblock(xblock)
         parent_category = parent_xblock.category if parent_xblock else None

cms/djangoapps/contentstore/xblock_storage_handlers/view_handlers.py

@@ -1278,7 +1278,7 @@ def create_xblock_info(  # lint-amnesty, pylint: disable=too-many-statements
         xblock_info.update(_get_gating_info(course, xblock))
         if is_xblock_unit:
             # if xblock is a Unit we add the discussion_enabled option
-            xblock_info["discussion_enabled"] = xblock.discussion_enabled
+            xblock_info["discussion_enabled"] = getattr(xblock, 'discussion_enabled', False)
 
             # Also add upstream info
             xblock_info["upstream_info"] = UpstreamLink.try_get_for_block(xblock).to_json()

cms/lib/xblock/upstream_sync.py

@@ -191,7 +191,7 @@ def get_for_block(cls, downstream: XBlock) -> t.Self:
                 container_meta = lib_api.get_container(upstream_key)
             except lib_api.ContentLibraryContainerNotFound as exc:
                 raise BadUpstream(_("Linked upstream library container was not found in the system")) from exc
-            expected_downstream_block_type = container_meta.container_type.olx_tag
+            expected_downstream_block_type = container_meta.container_type.value
             version_available = container_meta.published_version_num
 
         if downstream_type != expected_downstream_block_type: