Why can't I integrate the Java templating system Pebble?

It looks so simple

My pom.xml has:

        <repository>
            <id>sonatype-public</id>
            <name>Sonatype Public</name>
            <url>https://oss.sonatype.org/content/groups/public</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>

and

        <dependency>
            <groupId>io.pebbletemplates</groupId>
            <artifactId>pebble-spring-boot-starter</artifactId>
            <version>3.1.5</version>
        </dependency>

then I rm -rf ~/.m2/repository and mvn clean package compile but obviously still this bit of Kotlin is invalid:

package au.com.ngv.mystream.trove.view

val pebbleEngine = PebbleEngine.Builder().build()

HOWEVER I would expect IntelliJ after File / Invalidate caches ... to know what PebbleEngine is and suggest the right package to import, but IntelliJ shows PebbleEngine in red and offers only to create the class declaration. It does not offer to add the import declaration, which shows that it doesn't know from where PebbleEngine comes.

So why is it that after doing all that the Pebble documents say, I cannot use the package?