docs: add hint about how to reset an invitation

Author: r10s

deltachat-ffi/deltachat.h

@@ -2637,10 +2637,18 @@ dc_lot_t*       dc_check_qr                  (dc_context_t* context, const char*
  * DC_QR_ASK_VERIFYCONTACT, DC_QR_ASK_VERIFYGROUP or DC_QR_ASK_VERIFYBROADCAST
  * an out-of-band-verification can be joined using dc_join_securejoin()
  *
+ * If the device calling dc_check_qr() is the same device,
+ * #DC_QR_WITHDRAW_VERIFYCONTACT or #DC_QR_WITHDRAW_VERIFYGROUP will be returned instead,
+ * allowing to reset a QR code.
+ * By passing the resetted QR code again to dc_check_qr(), it finally can be revived.
+ * See dc_check_qr() for the detailed codes.
+ *
  * The returned text will also work as a normal https:-link,
  * so that the QR code is useful also without Delta Chat being installed
  * or can be passed to contacts through other channels.
  *
+ * To reset invitations, pass the link to dc_set_config_from_qr().
+ *
  * @memberof dc_context_t
  * @param context The context object.
  * @param chat_id If set to a group-chat-id,

deltachat-jsonrpc/src/api.rs

@@ -883,6 +883,8 @@ impl CommandApi {
 
     /// Get QR code text that will offer a [SecureJoin](https://securejoin.delta.chat/) invitation.
     ///
+    /// To reset invitations, pass the link to `set_config_from_qr()``.
+    ///
     /// If `chat_id` is a group chat ID, SecureJoin QR code for the group is returned.
     /// If `chat_id` is unset, setup contact QR code is returned.
     async fn get_chat_securejoin_qr_code(