Add explicit dependency on confluent_kafka (#139)

Author: noggi

datahub-actions/setup.py

@@ -67,7 +67,9 @@ def get_long_description():
 # Note: for all of these, framework_common will be added.
 plugins: Dict[str, Set[str]] = {
     # Source Plugins
-    "kafka": set(),  # included by default
+    "kafka": {
+        "confluent-kafka[schemaregistry]",
+    },
     # Action Plugins
     "executor": {
         "acryl-executor==0.1.2",