public static JoinGroupRequest parse(ByteBuffer buffer, short version) {
        return new JoinGroupRequest(new JoinGroupRequestData(new ByteBufferAccessor(buffer), version), version);
    }
Get the client's join reason.

@param request The JoinGroupRequest.

@return The join reason.
clients/src/main/java/org/apache/kafka/common/requests/JoinGroupRequest.java