utils/source-discoverer: Set the User-Agent

This avoids some web servers or WAFs doing weird stuff with our requests
which would lead to situations where our web calendar source discovery
would face server errors, redirects, incorrect contents, etc.

Fixes #651

Fixes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/290

src/utils/gcal-source-discoverer.c

@@ -281,7 +281,7 @@ discover_file_in_thread (DiscovererData  *data,
   uri_str = g_uri_to_string_partial (guri, G_URI_HIDE_PASSWORD);
   GCAL_TRACE_MSG ("Creating request for %s", uri_str);
 
-  session = soup_session_new_with_options ("timeout", 10, NULL);
+  session = gcal_create_soup_session ();
 
   message = soup_message_new_from_uri ("GET", guri);
   g_signal_connect (message, "authenticate", G_CALLBACK (on_soup_message_authenticate_cb), data);

src/utils/gcal-utils.c

@@ -32,6 +32,7 @@
 
 #include <libecal/libecal.h>
 #include <libedataserver/libedataserver.h>
+#include <libsoup/soup.h>
 
 #include <glib/gi18n.h>
 
@@ -1329,3 +1330,29 @@ gcal_get_service_name_from_url (const gchar *url)
 
   return NULL;
 }
+
+/**
+ * gcal_create_soup_session:
+ *
+* Creates a new #SoupSession with correct default settings.
+ *
+ * Returns: (transfer full): a new #SoupSession
+ */
+SoupSession *
+gcal_create_soup_session (void)
+{
+  g_autoptr (SoupSession) session = NULL;
+
+  session = soup_session_new ();
+
+  /* Set up a 10 seconds default timeout, as 60 is too long for fail-fast performance in general.
+   * Individual parts of the code can always override this if needed. */
+  soup_session_set_timeout (session, 10);
+
+  /* RFC2616 states HTTP requests "should" contain the User-Agent header. In practice though, in our situation
+   * User-Agent is mandatory, or restrictive "web application firewalls" can do unexpected things with our request.
+   * The trailing " - " lets libsoup append its name and version for us. */
+  soup_session_set_user_agent (session, "GNOME Calendar/" PACKAGE_VERSION " - ");
+
+  return g_steal_pointer (&session);
+}

src/utils/gcal-utils.h

@@ -139,4 +139,6 @@ gboolean             gcal_is_valid_event_name                    (const gchar
 
 const gchar*         gcal_get_service_name_from_url              (const gchar        *url);
 
+SoupSession *        gcal_create_soup_session                    (void);
+
 #endif /* __GCAL_UTILS_H__ */