fix when rejoining open groups messages sent were not loaded (case 4)

SignalServiceKit/src/Loki/API/Open Groups/LokiPublicChatPoller.swift

@@ -150,6 +150,7 @@ public final class LokiPublicChatPoller : NSObject {
                     if !wasSentByCurrentUser {
                         content.setDataMessage(try! dataMessage.build())
                     } else {
+                        SyncMessagesProtocol.addForceSyncMessageTimestamp(message.timestamp, from: senderHexEncodedPublicKey)
                         let syncMessageSentBuilder = SSKProtoSyncMessageSent.builder()
                         syncMessageSentBuilder.setMessage(try! dataMessage.build())
                         syncMessageSentBuilder.setDestination(userHexEncodedPublicKey)

SignalServiceKit/src/Loki/Protocol/Sync Messages/SyncMessagesProtocol.swift

@@ -96,6 +96,15 @@ public final class SyncMessagesProtocol : NSObject {
         let hexEncodedPublicKey = envelope.source!
         return LokiDatabaseUtilities.isUserLinkedDevice(hexEncodedPublicKey, transaction: transaction)
     }
+    
+    @objc(addForceSyncMessageTimestamp:from:)
+    public static func addForceSyncMessageTimestamp(_ timestamp: UInt64, from hexEncodedPublicKey: String) {
+        var timestamps: Set<UInt64> = syncMessageTimestamps[hexEncodedPublicKey] ?? []
+        if timestamps.contains(timestamp) {
+            timestamps.remove(timestamp)
+        }
+        syncMessageTimestamps[hexEncodedPublicKey] = timestamps
+    }
 
     // TODO: We should probably look at why sync messages are being duplicated rather than doing this
     @objc(isDuplicateSyncMessage:fromHexEncodedPublicKey:)