Represents a state change in a peer's subscription status. In this comment, the term "update" is used to refer to either a notification or an indication. This event is triggered by any of the following occurrences: o Peer enables or disables updates via a CCCD write. o Connection is about to be terminated and the peer is subscribed to updates. o Peer is now subscribed to updates after its state was restored from persistence. This happens when bonding is restored. Valid for the following event types: o BLE_GAP_EVENT_SUBSCRIBE