install plugins in kf<version>

CMakeLists.txt

 cmake_minimum_required(VERSION 3.16 FATAL_ERROR)
-set(PIM_VERSION "5.19.40")
+set(PIM_VERSION "5.19.41")
 project(MailTransport VERSION ${PIM_VERSION})
 
 # ECM setup

src/kmailtransport/plugins/smtp/CMakeLists.txt

 if (BUILD_TESTING)
     add_subdirectory(autotests)
 endif()
-kcoreaddons_add_plugin(mailtransport_smtpplugin JSON smtpmailtransport.json INSTALL_NAMESPACE mailtransport)
+kcoreaddons_add_plugin(mailtransport_smtpplugin JSON smtpmailtransport.json INSTALL_NAMESPACE "kf${QT_MAJOR_VERSION}/mailtransport")
 
 target_sources(mailtransport_smtpplugin PRIVATE
     smtpmailtransportplugin.cpp

src/kmailtransport/plugins/transportpluginmanager.cpp

@@ -55,7 +55,7 @@ void TransportPluginManagerPrivate::initializePlugins()
     if (!mPluginList.isEmpty()) {
         return;
     }
-    const QVector<KPluginMetaData> plugins = KPluginMetaData::findPlugins(QStringLiteral("mailtransport"));
+    const QVector<KPluginMetaData> plugins = KPluginMetaData::findPlugins(QStringLiteral("kf" QT_STRINGIFY(QT_VERSION_MAJOR) "/mailtransport"));
 
     QVectorIterator<KPluginMetaData> i(plugins);
     i.toBack();

src/kmailtransportakonadi/plugins/CMakeLists.txt

-kcoreaddons_add_plugin(mailtransport_akonadiplugin JSON akonadimailtransport.json INSTALL_NAMESPACE mailtransport)
+kcoreaddons_add_plugin(mailtransport_akonadiplugin JSON akonadimailtransport.json INSTALL_NAMESPACE "kf${QT_MAJOR_VERSION}/mailtransport")
 target_sources(mailtransport_akonadiplugin PRIVATE
     akonadimailtransportplugin.cpp
     resourcesendjob.cpp