Add an unknown USPS event code

lib/TrackingStatus.lib.php

@@ -177,6 +177,7 @@ class TrackingStatus {
             case "AP":
             case "CI": // stuck in customs
             case "AT": // departed a transfer airport (int'l)
+            case "A0": // "Acceptance" from foreign country
                 return TrackingStatus::TRACKING_STATUS_TRANSIT;
             case "01":
             case "13":
@@ -227,6 +228,7 @@ class TrackingStatus {
             case "TX":
                 return TrackingStatus::TRACKING_STATUS_FAILURE;
             default:
+                file_put_contents(__DIR__ . "/usps_unknown_events.log", "$eventcode\n", FILE_APPEND);
                 return TrackingStatus::TRACKING_STATUS_UNKNOWN;
         }
     }