DBus activation for IBus

This patch adds to the session the required DBus activation for
IBus, required to launch it when needed. It requires

canonical/core-base-desktop#19

snap/snapcraft.yaml

@@ -105,6 +105,30 @@ apps:
       activates-on:
         - dbus-freedesktop-impl-portal-gtk
 
+  ibus-service:
+    command: run.sh /usr/bin/ibus-daemon --panel disable
+    daemon: dbus
+    passthrough:
+      daemon-scope: user
+      activates-on:
+        - dbus-ibus
+
+  ibus-gtk3-service:
+    command: run.sh /usr/libexec/ibus-extension-gtk3
+    daemon: dbus
+    passthrough:
+      daemon-scope: user
+      activates-on:
+        - dbus-ibus-gtk3
+
+  ibus-portal-service:
+    command: run.sh /usr/libexec/ibus-portal
+    daemon: dbus
+    passthrough:
+      daemon-scope: user
+      activates-on:
+        - dbus-ibus-portal
+
 plugs:
   avahi-control: null
   bluez: null
@@ -357,6 +381,18 @@ slots:
     interface: dbus
     name: org.freedesktop.ReserveDevice1
     bus: session
+  dbus-ibus:
+    interface: dbus
+    name: org.freedesktop.IBus
+    bus: session
+  dbus-ibus-gtk3:
+    interface: dbus
+    name: org.freedesktop.IBus.Panel.Extension.Gtk3
+    bus: session
+  dbus-ibus-portal:
+    interface: dbus
+    name: org.freedesktop.portal.IBus
+    bus: session
 
 parts:
   scripts: