Empty mdc values still sent after upgrade to 2.0.0

[smlgbl]

trafficstars

Hi, we just upgraded to version 2.0.0, especially hoping to get the benefits of PR #300 - no more empty metadata, when e.g. a MDC field is sometimes empty. It seems, though, that the empty fields are still sent.

Here's the relevant part of our config:

<appender name="LOKI_INTERNAL" class="com.github.loki4j.logback.Loki4jAppender">
        <http>
            <url>${lokiEndpoint}</url>
        </http>
        <message class="com.github.loki4j.logback.JsonLayout">
            <loggerName>
                <enabled>false</enabled>
            </loggerName>
            <threadName>
                <enabled>false</enabled>
            </threadName>
            <timestamp>
                <enabled>false</enabled>
            </timestamp>
            <logLevel>
                <enabled>false</enabled>
            </logLevel>
            <mdc>
                <noPrefix>true</noPrefix>
                <exclude>offer_key</exclude>
            </mdc>
        </message>
        <labels>
            app = ${projectName}
            level = %level
            logger = %replace(%logger){'(\w)\w+\.', '$1.'}
            offer_key_start = %.-2mdc{offer_key}
        </labels>
        <structuredMetadata>
            thread = %thread
            host = ${HOSTNAME}
            offer_key = %mdc{offer_key}
            timestamp = %d{YYYY-MM-dd'T'HH:mm:ss.SSSZZ}
        </structuredMetadata>
</appender>

Are we doing something wrong? Did we misunderstand the PRs intention regarding issue #282 ?

Output in Loki:

Any help is appreciated and thanks for your hard work!