engine/order manager: Initial REST managed order updating (resolves #772) (#775)

* Initial REST managed order updating

* Apply gloriousCode's changes.go patch

* Update internal order ID handling

* Check error

* Replace string with string pointer

* Avoid nil pointers in upsert

* Update test for UpdateOrderFromDetail()

* Add tests for orders.go

* Remove unnecessary newline

* Address comments

* Add missing nil check

* Add tests for new functions in order_manager.go

* Remove empty line

* Change log level for updates from Info to Debug (keep added orders at Info)

* Initialize orders before running the timer

* [TEMP] Add verbosity for debugging

* Nil checking on exchangeManager in GetExchanges()

- exchangeManager.GetExchanges() and iExchangeManager.GetExchanges() return an error on nil
- bot.GetExchanges() wraps exchangeManager.GetExchanges() and returns an empty slice

* Revert b5afe1a46b

* Do not start the order manager runner thread

Instead, mark the order manager as running

* Remove redundant error.Is() and remove print wrapper on msg

* Add atomic blocker and waitgroup on processOrders()

* Disable unnecessary orderManager runner thread for rpcserver_test

* Remove redundant err from orderStore.getActiveOrders()

* [FIX] Populate requiresProcessing using UpsertResponse data instead of REST return data

.. because the data returned by the REST calls do not include the internal user ID's

* [TEST] Verify that processOrders() actually processes queried order data

* Remove leftover warning and add nil check on wg.Done()

* Apply suggestions from code review

Log category changes - as suggested

Co-authored-by: Adrian Gallagher <adrian.gallagher@thrasher.io>

* Return when no exchanges available

Co-authored-by: Adrian Gallagher <adrian.gallagher@thrasher.io>

engine/sync_manager.go

@@ -104,7 +104,10 @@ func (m *syncManager) Start() error {
 	m.initSyncWG.Add(1)
 	m.inService.Done()
 	log.Debugln(log.SyncMgr, "Exchange CurrencyPairSyncer started.")
-	exchanges := m.exchangeManager.GetExchanges()
+	exchanges, err := m.exchangeManager.GetExchanges()
+	if err != nil {
+		return err
+	}
 	for x := range exchanges {
 		exchangeName := exchanges[x].GetName()
 		supportsWebsocket := exchanges[x].SupportsWebsocket()
@@ -454,7 +457,10 @@ func (m *syncManager) worker() {
 	defer cleanup()
 
 	for atomic.LoadInt32(&m.started) != 0 {
-		exchanges := m.exchangeManager.GetExchanges()
+		exchanges, err := m.exchangeManager.GetExchanges()
+		if err != nil {
+			log.Errorf(log.SyncMgr, "Sync manager cannot get exchanges: %v", err)
+		}
 		for x := range exchanges {
 			exchangeName := exchanges[x].GetName()
 			supportsREST := exchanges[x].SupportsREST()