How to include inner json object

[vladigeras]

Thank you for project!

I would like to send logs by next structure:

{
  "event": {
    "severity": "INFO",
    "message": {
      "correlationId": "9df8d06b7d3f0c42bf2d81fbc976a6c1",
      "system": "WebApi"
    }
  }
}

And I send logs like this:

<appender name="ELASTIC" class="com.internetitem.logback.elasticsearch.ElasticsearchAppender">
  <url>http://localhost:9200/_bulk</url>
  <index>logs</index>
  <properties>
     <property>
          <name>event</name>
          <value>
              <property>
                  <name>severity</name>
                  <value>%level</value>
              </property>
              <property>
                  <name>message</name>
                  <value>
                      <property>
                          <name>correlationId</name>
                          <value>correlationId</value>
                       </property>
                       <property>
                          <name>system</name>
                          <value>system</value>
                       </property>
                  </value>
              </property>
          </value>
      </property>
  </properties>
  <headers>
    <header>
        <name>Content-Type</name>
	<value>application/json</value>
    </header>
  </headers>
</appender>

I get the next error

ERROR in ch.qos.logback.core.joran.spi.Interpreter@45:18 - no applicable action for [property], current ElementPath  is [[configuration][appender][properties][property][value][property][value][property]]

I think, this is incorrect approach. How can I do it?