add update shipments

lib/pages/shipment/model/shipment_model.dart

@@ -117,6 +117,7 @@ class ShipmentModel extends BaseModel {
       var q = Firestore.instance
           .collection("$path")
           .where("is_delivered", isEqualTo: false)
+          .where("is_canceled", isEqualTo: false)
           .where("is_deleted", isEqualTo: false);
 
       if (forCustomer) {
@@ -144,6 +145,21 @@ class ShipmentModel extends BaseModel {
     shipment_courier_dropoff
   ];
 
+  Future<Shipment> getShipment(String shipmentID) async {
+    String path = "/$shipments_collection";
+    try {
+      var ref = Firestore.instance.collection("$path").document(shipmentID);
+      var snap = await ref.get(source: Source.server);
+      if (snap.exists) {
+        var s = Shipment.fromMap(snap.data, snap.documentID);
+        return s;
+      }
+    } catch (e) {
+      log.warning("Error!! $e");
+    }
+    return null;
+  }
+
   void initUser(user) {
     super.initUser(user);
   }
@@ -155,4 +171,8 @@ class ShipmentModel extends BaseModel {
   Future<void> updateShipment(Shipment shipment) {
     return Services.instance.shipmentService.updateShipment(shipment);
   }
+
+  Future<void> cancelShipment(Shipment shipment) {
+    return Services.instance.shipmentService.cancelShipment(shipment);
+  }
 }