fix(mps-model-server-plugin): use startupActivity instead of AppLifecycleListener

AppLifecycleListener.appStarting doesn't exist in MPS 2020.3
and .appStarting is internal API.
It's anyway recommended to use a startupActivity instead.
See https://plugins.jetbrains.com/docs/intellij/plugin-components.html#project-open

Author: slisson

mps-model-server-plugin/src/main/kotlin/org/modelix/model/server/mps/MPSModelServer.kt

@@ -13,14 +13,14 @@
  */
 package org.modelix.model.server.mps
 
-import com.intellij.ide.AppLifecycleListener
 import com.intellij.ide.plugins.DynamicPluginListener
 import com.intellij.ide.plugins.IdeaPluginDescriptor
 import com.intellij.openapi.Disposable
 import com.intellij.openapi.components.Service
 import com.intellij.openapi.components.service
 import com.intellij.openapi.project.DumbService
 import com.intellij.openapi.project.Project
+import com.intellij.openapi.startup.StartupActivity
 import jetbrains.mps.ide.project.ProjectHelper
 import jetbrains.mps.project.ProjectBase
 import jetbrains.mps.project.ProjectManager
@@ -127,12 +127,8 @@ class MPSModelServerDynamicPluginListener : DynamicPluginListener {
     }
 }
 
-class MPSModelServerAppLifecycleListener : AppLifecycleListener {
-    override fun appStarting(projectFromCommandLine: Project?) {
-        service<MPSModelServer>().ensureStarted()
-    }
-
-    override fun appStarted() {
+class MPSModelServerStartupActivity : StartupActivity {
+    override fun runActivity(project: Project) {
         service<MPSModelServer>().ensureStarted()
     }
 }

mps-model-server-plugin/src/main/resources/META-INF/plugin.xml

@@ -25,14 +25,11 @@
         <listener
                 class="org.modelix.model.server.mps.MPSModelServerDynamicPluginListener"
                 topic="com.intellij.ide.plugins.DynamicPluginListener"/>
-        <listener
-                class="org.modelix.model.server.mps.MPSModelServerAppLifecycleListener"
-                topic="com.intellij.ide.AppLifecycleListener"/>
     </applicationListeners>
 
     <!-- Extension points defined by the plugin.
          Read more: https://plugins.jetbrains.com/docs/intellij/plugin-extension-points.html -->
     <extensions defaultExtensionNs="com.intellij">
-
+        <postStartupActivity implementation="org.modelix.model.server.mps.MPSModelServerStartupActivity" />
     </extensions>
 </idea-plugin>