emqx5.7 如何配置消息持久化？

4.0配置如下：

retainer {

## set to false to disable retainer

enable = true

## Message retention time, default is 0 means the message will never expire

msg_expiry_interval = 5s

## Maximum message size allowed

max_payload_size = 1MB

## When the retained flag of the PUBLISH message is set and Payload is empty, whether to continue to publish the message

stop_publish_clear_msg = false

## Maximum retained messages delivery rate per session

delivery_rate = "1000/s"

## Retained messages store backend

backend {

## Built-in database (Mnesia)

type = built_in_database

## Specifies whether the messages are stored in RAM or persisted on disk

## Type: enum: ram | disc

storage_type = disc

## Maximum number of retained messages. 0 means no limit

max_retained_messages = 0

}

}

5.0应该如何配置？