plugin.xml

<!-- Plugin Configuration File. Read more: https://plugins.jetbrains.com/docs/intellij/plugin-configuration-file.html -->
<idea-plugin>
    <id>com.github.tab.testplugin</id>
    <name>TestPlugin</name>
    <vendor>t-a-b</vendor>

    <depends>com.intellij.modules.platform</depends>

    <extensions defaultExtensionNs="com.intellij">
        <applicationService serviceImplementation="com.github.tab.testplugin.services.MyApplicationService"/>
        <projectService serviceImplementation="com.github.tab.testplugin.services.MyProjectService"/>
    </extensions>

    <applicationListeners>
        <listener class="com.github.tab.testplugin.listeners.MyProjectManagerListener"
                  topic="com.intellij.openapi.project.ProjectManagerListener"/>
    </applicationListeners>
</idea-plugin>