print: add two new capabilities (n-copies and number-up)

Both the app and the printer may be able to do copies. If the printer
can do it, then it is likely more efficient and it should not be done in the app,
so the app needs to know that the printer will do it.

In the print dialog, the n-copies and number-up settings must be available
if either the printer or the app can do it.

Author: lbaudin

data/org.freedesktop.portal.Print.xml

@@ -34,7 +34,7 @@
       to print the formatted document. It is expected that high-level toolkit
       APIs such as GtkPrintOperation will hide most of this complexity.
 
-      This documentation describes version 4 of this interface.
+      This documentation describes version 5 of this interface.
   -->
   <interface name="org.freedesktop.portal.Print">
     <!--
@@ -86,6 +86,19 @@
 
           This option was added in version 4.
 
+        * ``has_n_copies`` (``b``)
+
+          Whether the app is able to manually implement the n-copies and collate settings.
+
+          This option was added in version 5.
+
+        * ``has_number_up`` (``b``)
+
+          Whether the app is able to manually implement the number-up and number-up-layout setting.
+
+          This option was added in version 5.
+
+
         The @settings and @page_setup vardict contain hints for the initial state of the print dialog.
 
         The following keys are supported in the @settings vardict:
@@ -254,7 +267,22 @@
 
           Print settings as set up by the user in the print dialog. The same keys as in @settings
           are supported (see above).
+        * ``printer-info`` (``a{sv}``)
+
+          Printer information with the following keys:
+
+          * ``has-n-copies`` (``b``)
+
+            Whether the printer has the n-copies capability. In this case, the app should not provide
+            a document with multiple copies if it has set has_n_copies to true in @options.
+           
+          * ``has-number-up`` (``b``)
 
+            Whether the printer has the n-up capability. In this case, the app should not provide
+            a document with pages per side if it has set has_n_up to true in @options.
+            
+          This option was added in version 5.
+           
         * ``page-setup`` (``a{sv}``)
 
           Page setup as set up by the user in the print dialog. The same keys as in @page_setup

src/print.c

@@ -210,6 +210,7 @@ handle_print (XdpDbusPrint *object,
 static XdpOptionKey response_options[] = {
   { "settings", G_VARIANT_TYPE_VARDICT, NULL },
   { "page-setup", G_VARIANT_TYPE_VARDICT, NULL },
+  { "printer-info", G_VARIANT_TYPE_VARDICT, NULL },
   { "token", G_VARIANT_TYPE_UINT32, NULL }
 };
 
@@ -259,6 +260,8 @@ static XdpOptionKey prepare_print_options[] = {
   { "supported_output_file_formats", G_VARIANT_TYPE_STRING_ARRAY, validate_supported_output_file_formats },
   { "has_current_page", G_VARIANT_TYPE_BOOLEAN },
   { "has_selected_pages", G_VARIANT_TYPE_BOOLEAN },
+  { "has_n_copies", G_VARIANT_TYPE_BOOLEAN },
+  { "has_number_up", G_VARIANT_TYPE_BOOLEAN },
 };
 
 static gboolean