feat: adds component_key to LibraryXBlockMetadata

and its serializer so the frontend has component_keys for use with the
/collection/contents endpoint.

openedx/core/djangoapps/content_libraries/api.py

@@ -206,6 +206,7 @@ class LibraryXBlockMetadata:
     last_published = attr.ib(default=None, type=datetime)
     has_unpublished_changes = attr.ib(False)
     tags_count = attr.ib(0)
+    component_key = attr.ib(default=None, type=str)
 
     @classmethod
     def from_component(cls, library_key, component):
@@ -215,6 +216,7 @@ def from_component(cls, library_key, component):
         last_publish_log = component.versioning.last_publish_log
 
         return cls(
+            component_key=component.key,
             usage_key=LibraryUsageLocatorV2(
                 library_key,
                 component.component_type.name,

openedx/core/djangoapps/content_libraries/serializers.py

@@ -152,6 +152,9 @@ class LibraryXBlockMetadataSerializer(serializers.Serializer):
     slug = serializers.CharField(write_only=True)
     tags_count = serializers.IntegerField(read_only=True)
 
+    # Key for the Component / PublishableEntity associated with this XBlock
+    component_key = serializers.CharField(read_only=True)
+
 
 class LibraryXBlockTypeSerializer(serializers.Serializer):
     """

openedx/core/djangoapps/content_libraries/tests/test_content_libraries.py

@@ -1020,6 +1020,7 @@ def test_library_paste_clipboard(self):
             self.assertDictContainsEntries(self._get_library_block(paste_data["id"]), {
                 **block_data,
                 "id": f"lb:CL-TEST:test_lib_paste_clipboard:problem:{pasted_block_id}",
+                "component_key": f"xblock.v1:problem:{pasted_block_id}",
             })