AKCORE-81: Experiment with read-committed share groups

clients/src/main/resources/common/message/ShareFetchResponse.json

@@ -52,6 +52,13 @@
             "The last offset of this batch of acquired records." },
           { "name": "DeliveryCount", "type": "int16", "versions": "0+",
             "about": "The delivery count of this batch of acquired records." }
+        ]},
+        { "name": "AbortedTransactions", "type": "[]AbortedTransaction", "versions": "0+", "nullableVersions": "0+", "ignorable": true,
+          "about": "The aborted transactions.",  "fields": [
+          { "name": "ProducerId", "type": "int64", "versions": "0+", "entityType": "producerId",
+            "about": "The producer id associated with the aborted transaction." },
+          { "name": "FirstOffset", "type": "int64", "versions": "0+",
+            "about": "The first offset in the aborted transaction." }
         ]}
       ]}
     ]},

clients/src/main/resources/common/message/ShareGroupHeartbeatResponse.json

@@ -40,6 +40,8 @@
       "about": "The member epoch." },
     { "name": "HeartbeatIntervalMs", "type": "int32", "versions": "0+",
       "about": "The heartbeat interval in milliseconds." },
+    { "name": "IsolationLevel", "type": "int8", "versions": "0+", "default": "0", "ignorable": true,
+      "about": "This setting controls the visibility of transactional records. Using READ_UNCOMMITTED (isolation_level = 0) makes all records visible. With READ_COMMITTED (isolation_level = 1), non-transactional and COMMITTED transactional records are visible. To be more concrete, READ_COMMITTED returns all data from offsets smaller than the current LSO (last stable offset), and enables the inclusion of the list of aborted transactions in the result, which allows consumers to discard ABORTED transactional records" },
     { "name": "Assignment", "type": "Assignment", "versions": "0+", "nullableVersions": "0+", "default": "null",
       "about": "null if not provided; the assignment otherwise.", "fields": [
       { "name": "Error", "type": "int8", "versions": "0+",