Logback with logstash-logback-encoder: RegexValueMasker usage in order to mask values

Question

I want to mask sensitive values in log messages by using standard RegexValueMasker instead of writing custom one.

MaskingJsonGeneratorDecorator was added to my logback.xml file, but there is lack in documentation: https://github.com/logfellow/logstash-logback-encoder#masking

According to RegexValueMasker implementation I can pass regex pattern into logback.xml, is there a chance to get some sample usage of above mentioned ValueMasker.

<encoder class="net.logstash.logback.encoder.LogstashEncoder">
    <jsonGeneratorDecorator class="net.logstash.logback.mask.MaskingJsonGeneratorDecorator">
        <defaultMask>****</defaultMask>
        <value>regex-expression</value> // ???
        <valueMasker class="net.logstash.logback.mask.RegexValueMasker"/>
    </jsonGeneratorDecorator>

    <!-- because of https://github.com/logstash/logstash-logback-encoder/issues/387 -->
    <findAndRegisterJacksonModules>false</findAndRegisterJacksonModules>
</encoder>