fix: allow adding own JID to roster (upstream 4c731f52)

src/xmpp/resource.h

@@ -48,6 +48,7 @@ typedef struct resource_t
 
 Resource* resource_new(const char* const name, resource_presence_t presence, const char* const status,
                        const int priority);
+Resource* resource_copy(Resource* resource);
 void resource_destroy(Resource* resource);
 int resource_compare_availability(Resource* first, Resource* second);