fix: allow adding own JID to roster

Enable adding oneself to the roster.

Self subscriptions are implicit according to XEP-0060 / XEP-0163.
So we adapt the /sub command to handle this gracefully by just printing
an informative message.

Profanitys logic didn't handle own presence/when adding to roster
correctly. This got fixed now.

Fixes: https://github.com/profanity-im/profanity/issues/2084

Signed-off-by: Michael Vetter <jubalh@iodoru.org>

src/xmpp/resource.c

@@ -75,6 +75,16 @@ resource_destroy(Resource* resource)
     }
 }
 
+Resource*
+resource_copy(Resource* resource)
+{
+    if (resource == NULL) {
+        return NULL;
+    }
+
+    return resource_new(resource->name, resource->presence, resource->status, resource->priority);
+}
+
 gboolean
 valid_resource_presence_string(const gchar* const str)
 {