notify: add typesafe notifications

damus/Notify/LogoutNotify.swift

@@ -0,0 +1,26 @@
+//
+//  LogoutNotify.swift
+//  damus
+//
+//  Created by William Casarin on 2023-07-30.
+//
+
+import Foundation
+
+struct LogoutNotify: Notify {
+    typealias Payload = ()
+    var payload: ()
+}
+
+extension NotifyHandler {
+    static var logout: NotifyHandler<LogoutNotify> {
+        .init()
+    }
+}
+
+extension Notifications {
+    /// Sign out of damus. Goes back to the login screen.
+    static var logout: Notifications<LogoutNotify> {
+        .init(.init(payload: ()))
+    }
+}