core/context: Delay reading time format

Reading time format from the settings portal during context init results
in interacting with xdg-desktop-portal before GtkApplication can
register the host app id. This makes portals not aware of the
application id, which could cause problems in the future.

Fix that by calling read_time_format during gcal_context_startup, which
is called after the GtkApplication startup chain-up.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/586>

src/core/gcal-context.c

@@ -331,14 +331,6 @@ gcal_context_init (GcalContext *self)
 
   if (error)
     g_error ("Failed to load portals: %s. Aborting...", error->message);
-
-  if (read_time_format (self))
-    {
-      g_signal_connect (self->settings_portal,
-                        "g-signal",
-                        G_CALLBACK (on_portal_proxy_signal_cb),
-                        self);
-    }
 }
 
 /**
@@ -465,5 +457,13 @@ gcal_context_startup (GcalContext *self)
 {
   g_return_if_fail (GCAL_IS_CONTEXT (self));
 
+  if (read_time_format (self))
+    {
+      g_signal_connect (self->settings_portal,
+                        "g-signal",
+                        G_CALLBACK (on_portal_proxy_signal_cb),
+                        self);
+    }
+
   gcal_manager_startup (self->manager);
 }