java-tutorials/maven-polyglot/maven-polyglot-yml-app/.mvn/extensions.xml

<?xml version="1.0" encoding="UTF-8"?>
<extensions>
    <extension>
        <groupId>io.takari.polyglot</groupId>
        <artifactId>polyglot-yaml</artifactId>
        <version>0.3.1</version>
    </extension>
</extensions>