pom-all-open.xml

<plugin>
    <artifactId>kotlin-maven-plugin</artifactId>
    <groupId>org.jetbrains.kotlin</groupId>
    <configuration>
        <compilerPlugins>
            <plugin>all-open</plugin>
        </compilerPlugins>
        <pluginOptions>
            <option>all-open:annotation=org.craftsrecords.hexarch.DomainService</option>
            <option>all-open:annotation=org.craftsrecords.hexarch.Stub</option>
        </pluginOptions>
    </configuration>
    <dependencies>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-maven-allopen</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
    </dependencies>
</plugin>