xdg_activation: determine seat for a given token

An xdg activation token allows activating a surface. However, it's not possible to determine to which seat this token belongs. E.g.: Typically, when a user starts a client via the launcher, an activation token is passed to it. This token may be used by this client or passed to an existing client. However, neither of these clients can determine which seat initiated the action.

My user case is rendering an layer-shell overlay that should only react to actions from that seat. I can imagine other potential use cases may arise for applications that have actual multi-seat support. For example, a game when launched by a second seat might want to add a player 2 for that seat to an existing instance (or at least prompt to?).

Could a new request be added to xdg-activation-v1::xdg_activation_v1? This would take the token as input and somehow yield the corresponding seat's id. Or would an extension protocol be best?