消息中的data字段列表中能不能只存放一条记录

## Question

"data":[{"id":"100","memo":"123","update_time":"2020-09-03 16:30:11","name":"xxx"},{"id":"200","memo":"456","update_time":"2020-09-03 16:30:11","name":"xxx"}]
当insert语句有多个values时，消息中data也是多个，使用flink计算计数很麻烦~

No files, tests, or entry points are named. First confirm how Canal represents a multi-value INSERT in its message data and how that format is consumed by Flink; done means the requested single-record representation is clearly defined and its compatibility impact is understood.

Written by the indexing model from the issue text.