Optional dependencies in Maven

consumer-pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.acme</groupId>
  <artifactId>consumer</artifactId>
  <version>1.0.0</version>

  <dependencies>
    <dependency>
      <groupId>com.acme</groupId>
      <artifactId>producer</artifactId>
      <version>1.0.0</version>
    </dependency>
  </dependencies>
</project>

producer-pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.acme</groupId>
  <artifactId>producer</artifactId>
  <version>1.0.0</version>

  <dependencies>
    <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-lang3</artifactId>
      <version>3.10</version>
    </dependency>
    <dependency>
      <groupId>com.google.guava</groupId>
      <artifactId>guava</artifactId>
      <version>29.0-jre</version>
      <optional>true</optional>
    </dependency>
  </dependencies>
</project>