Simplify deviceMessages method

no need for a callback as it's a sync method.

// FREEBIE

src/Messages/TSMessagesManager+sendMessages.m

@@ -236,13 +236,10 @@ dispatch_queue_t sendingQueue() {
     if (remainingAttempts > 0) {
         remainingAttempts -= 1;
 
-        [self outgoingMessages:message
-                   toRecipient:recipient
-                      inThread:thread
-                    completion:^(NSArray *messages) {
-                      TSSubmitMessageRequest *request =
-                          [[TSSubmitMessageRequest alloc] initWithRecipient:recipient.uniqueId
-                                                                   messages:messages
+        NSArray<NSDictionary *> *deviceMessages = [self deviceMessages:message forRecipient:recipient inThread:thread];
+
+        TSSubmitMessageRequest *request = [[TSSubmitMessageRequest alloc] initWithRecipient:recipient.uniqueId
+                                                                                   messages:deviceMessages
                                                                                       relay:recipient.relay
                                                                                   timeStamp:message.timestamp];
 
@@ -274,8 +271,7 @@ dispatch_queue_t sendingQueue() {
                             [NSJSONSerialization JSONObjectWithData:responseData options:0 error:&e];
 
                         if (e) {
-                                        DDLogError(@"Failed to serialize response of mismatched devices: %@",
-                                                   e.description);
+                            DDLogError(@"Failed to serialize response of mismatched devices: %@", e.description);
                         } else {
                             [self handleMismatchedDevices:serializedResponse recipient:recipient];
                         }
@@ -323,7 +319,6 @@ dispatch_queue_t sendingQueue() {
                         break;
                 }
             }];
-                    }];
     } else {
         [self saveMessage:message withState:TSOutgoingMessageStateUnsent];
         BLOCK_SAFE_RUN(failureBlock);
@@ -356,10 +351,10 @@ dispatch_queue_t sendingQueue() {
     [self saveMessage:message withState:TSOutgoingMessageStateSent];
 }
 
-- (void)outgoingMessages:(TSOutgoingMessage *)message
-             toRecipient:(SignalRecipient *)recipient
+- (NSArray<NSDictionary *> *)deviceMessages:(TSOutgoingMessage *)message
+                               forRecipient:(SignalRecipient *)recipient
                                    inThread:(TSThread *)thread
-              completion:(messagesQueue)sendMessages {
+{
     NSMutableArray *messagesArray = [NSMutableArray arrayWithCapacity:recipient.devices.count];
     TSStorageManager *storage     = [TSStorageManager sharedManager];
     NSData *plainText             = [self plainTextForMessage:message inThread:thread];
@@ -381,13 +376,13 @@ dispatch_queue_t sendingQueue() {
             if ([exception.name isEqualToString:InvalidDeviceException]) {
                 [recipient removeDevices:[NSSet setWithObject:deviceNumber]];
             } else {
+                DDLogWarn(@"Failed building message for device: %@ withe error %@", deviceNumber, exception);
                 [self processException:exception outgoingMessage:message inThread:thread];
-                return;
             }
         }
     }
 
-    sendMessages(messagesArray);
+    return [messagesArray copy];
 }
 
 - (NSDictionary *)encryptedMessageWithPlaintext:(NSData *)plainText