configuration accepted for kakfa

src/testdata/config-kafka-to-stdout.yaml

@@ -0,0 +1,11 @@
+streams:
+  input:
+    engine:
+      name: kafka
+      kafka:
+        topic: xyz
+        consumer_group: uvw
+  output:
+    engine:
+      name: stdout
+

src/testdata/config-kinesis-to-kafka.json

@@ -13,7 +13,8 @@
          "engine": {
             "name": "kafka",
             "kafka": {
-               "topic": "topic-name"
+               "topic": "topic-name",
+               "consumer_group": "consumer-group-name"
             }
          }
       }