DBus: Use org.gnome prefix and adapt to changes

In preparation to moving to GNOME all the IDs, DBus object paths, etc should
change.

src/dbus/org.gnome.Calls.Call.xml

@@ -0,0 +1,39 @@
+<!DOCTYPE node PUBLIC
+        "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN"
+        "http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
+
+<!--
+        Copyright (C) 2021 Purism SPC
+
+        This library is free software; you can redistribute it and/or
+        modify it under the terms of the GNU Lesser General Public
+        License as published by the Free Software Foundation; either
+        version 3 of the License, or (at your option) any later version.
+
+        This library is distributed in the hope that it will be useful,
+        but WITHOUT ANY WARRANTY; without even the implied warranty of
+        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+        Lesser General Public License for more details.
+
+        You should have received a copy of the GNU Lesser General
+        Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+-->
+
+<node>
+
+  <interface name="org.gnome.Calls.Call">
+    <method name="Accept"/>
+    <method name="Hangup"/>
+    <property name="Inbound" type="b" access="read"/>
+    <property name="State" type="u" access="read"/>
+    <property name="Id" type="s" access="read">
+      <doc:doc>
+        <doc:description>
+          <doc:para>The Id identifying the call, e.g. a phone number</doc:para>
+        </doc:description>
+      </doc:doc>
+    </property>
+    <property name="Party" type="s" access="read"/>
+  </interface>
+
+</node>