feat: Add event listener for course publish

Creates the edx-platform plugin plumbing, adds some new requirements, maps the appropriate Django Signal to push course structure to ClickHouse.

event_sink_clickhouse/settings/common.py

@@ -9,7 +9,8 @@ def plugin_settings(settings):
     """
     settings.EVENT_SINK_CLICKHOUSE_BACKEND_CONFIG = {
         # URL to a running ClickHouse server's HTTP interface. ex: https://foo.openedx.org:8443/ or
-        # http://foo.openedx.org:8123/
+        # http://foo.openedx.org:8123/ . Note that we only support the ClickHouse HTTP interface
+        # to avoid pulling in more dependencies to the platrform than necessary.
         "url": "http://clickhouse:8123",
         "username": "changeme",
         "password": "changeme",

event_sink_clickhouse/signals.py

@@ -10,5 +10,4 @@ def receive_course_publish(sender, course_key, **kwargs):  # pylint: disable=unu
     # import here, because signal is registered at startup, but items in tasks are not yet able to be loaded
     from .tasks import dump_course_to_clickhouse  # pylint: disable=import-outside-toplevel
 
-    course_key_str = str(course_key)
-    dump_course_to_clickhouse.delay(course_key_str)
+    dump_course_to_clickhouse.delay(str(course_key))

event_sink_clickhouse/sinks/course_published.py

@@ -100,8 +100,8 @@ def serialize_course(self, course_id):
             course_id: CourseKey of the course we want to serialize
 
         Returns:
-            nodes: a csv of nodes for the course
-            relationships: a csv of relationships between nodes
+            nodes: a list of dicts representing xblocks for the course
+            relationships: a list of dicts representing relationships between nodes
         """
         # Import is placed here to avoid model import at project startup.
         from xmodule.modulestore.django import modulestore  # pylint: disable=import-outside-toplevel,import-error