Include attachment IDs in public chat message signature

SignalServiceKit/src/Loki/API/Public Chat/LokiPublicChatMessage.swift

@@ -29,6 +29,7 @@ public final class LokiPublicChatMessage : NSObject {
     }
     
     public struct Attachment {
+        public let serverID: UInt64
         public let kind: Kind
         public let width: UInt
         public let height: UInt
@@ -121,9 +122,9 @@ public final class LokiPublicChatMessage : NSObject {
     }
     
     // MARK: Convenience
-    @objc public func addAttachment(kind: String, width: UInt, height: UInt, caption: String, url: String, server: String, serverDisplayName: String) {
+    @objc public func addAttachment(serverID: UInt64, kind: String, width: UInt, height: UInt, caption: String, url: String, server: String, serverDisplayName: String) {
         guard let kind = Attachment.Kind(rawValue: kind) else { preconditionFailure() }
-        let attachment = Attachment(kind: kind, width: width, height: height, caption: caption, url: url, server: server, serverDisplayName: serverDisplayName)
+        let attachment = Attachment(serverID: serverID, kind: kind, width: width, height: height, caption: caption, url: url, server: server, serverDisplayName: serverDisplayName)
         attachments.append(attachment)
     }
     
@@ -135,6 +136,7 @@ public final class LokiPublicChatMessage : NSObject {
                 string += "\(quotedMessageServerID)"
             }
         }
+        string += attachments.map { "\($0.serverID)" }.joined(separator: "")
         string += "\(signatureVersion)"
         return string.data(using: String.Encoding.utf8)
     }

SignalServiceKit/src/Messages/OWSMessageSender.m

@@ -1214,7 +1214,7 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
             TSAttachmentStream *attachment = [TSAttachmentStream fetchObjectWithUniqueID:attachmentID];
             if (attachment == nil) { continue; }
             // TODO: Videos
-            [groupMessage addAttachmentWithKind:@"photo" width:@(attachment.imageSize.width).unsignedIntValue height:@(attachment.imageSize.height).unsignedIntValue caption:attachment.caption url:attachment.downloadURL server:publicChat.server serverDisplayName:publicChat.displayName];
+            [groupMessage addAttachmentWithServerID:attachment.serverId kind:@"photo" width:@(attachment.imageSize.width).unsignedIntValue height:@(attachment.imageSize.height).unsignedIntValue caption:attachment.caption url:attachment.downloadURL server:publicChat.server serverDisplayName:publicChat.displayName];
         }
         [[LKPublicChatAPI sendMessage:groupMessage toGroup:publicChat.channel onServer:publicChat.server]
         .thenOn(OWSDispatch.sendingQueue, ^(LKGroupMessage *groupMessage) {