NostrEvent: add local flags for internal use

Signed-off-by: William Casarin <jb55@jb55.com>

damus/Nostr/NostrEvent.swift

@@ -27,6 +27,9 @@ class NostrEvent: Codable, Identifiable {
     // cached field for pow calc
     var pow: Int?
 
+    // custom flags for internal use
+    var flags: Int = 0
+
     let pubkey: String
     let created_at: Int64
     let kind: Int
@@ -36,6 +39,17 @@ class NostrEvent: Codable, Identifiable {
         case id, sig, tags, pubkey, created_at, kind, content
     }
 
+    /// Make a local event
+    public static func local(content: String, pubkey: String) -> NostrEvent {
+        let ev = NostrEvent(content: content, pubkey: pubkey)
+        ev.flags |= 1
+        return ev
+    }
+
+    public var is_local: Bool {
+        return (self.flags & 1) != 0
+    }
+
     init(content: String, pubkey: String, kind: Int = 1, tags: [[String]] = []) {
         self.id = ""
         self.sig = ""