private Struct buildRecordValue() {
        Struct struct = new Struct(END_TXN_MARKER_SCHEMA_VERSION_V0);
        struct.set("version", CURRENT_END_TXN_MARKER_VERSION);
        struct.set("coordinator_epoch", coordinatorEpoch);
        return struct;
    }
This class represents the control record which is written to the log to indicate the completion
of a transaction. The record key specifies the {@link ControlRecordType control type} and the
value embeds information useful for write validation (for now, just the coordinator epoch).
clients/src/main/java/org/apache/kafka/common/record/EndTransactionMarker.java