Sales order support (#438)

* Add new models for SalesOrder

- Create generic Order and OrderLine models with common functionality

* Refactor

- Move some widgets around
- Cleanup directory structure

* Add link to home screen and nav drawer

* Add SalesOrder list widget

* Linting fixes

* Fix string

* Refactor PurchaseOrderDetailWidget

* Tweaks to existing code

* linting

* Fixes for drawer widget

* Add "detail" page for SalesOrder

* Add more tiles to SalesOrder detail

* Allow editing of salesorder

* add list filters for sales orders

* Display list of line items

* Customer updates

- Display customer icon on home screen
- Fetch sales orders for customer detail page

* Cleanup company detail view

* Create new sales order from list

* Stricter typing for formFields method

* Create new PurchaseOrder and SalesOrder from company deatil

* Status code updates

- Add function for name comparison
- Remove hard-coded values

* Update view permission checks for home widget

* Add ability to manually add SalesOrderLineItem

* Add nice progress bar widgets

* Display detail view for sales order line item

* edit SalesOrderLineItem

* Fix unused import

* Hide "shipped items" tab

- Will be added in a future update

lib/api.dart

@@ -620,6 +620,8 @@ class InvenTreeAPI {
     _globalSettings.clear();
     _userSettings.clear();
 
+    roles.clear();
+    _plugins.clear();
     serverInfo.clear();
     _connectionStatusChanged();
   }
@@ -672,6 +674,8 @@ class InvenTreeAPI {
 
     _connectionStatusChanged();
 
+    fetchStatusCodeData();
+
     return _connected;
   }
 
@@ -735,6 +739,10 @@ class InvenTreeAPI {
    */
   bool checkPermission(String role, String permission) {
 
+    if (!_connected) {
+      return false;
+    }
+
     // If we do not have enough information, assume permission is allowed
     if (roles.isEmpty) {
       debug("checkPermission - no roles defined!");
@@ -1624,11 +1632,20 @@ class InvenTreeAPI {
   InvenTreeStatusCode get StockHistoryStatus => _get_status_class("stock/track/status/");
   InvenTreeStatusCode get StockStatus => _get_status_class("stock/status/");
   InvenTreeStatusCode get PurchaseOrderStatus => _get_status_class("order/po/status/");
+  InvenTreeStatusCode get SalesOrderStatus => _get_status_class("order/so/status/");
 
   void clearStatusCodeData() {
     StockHistoryStatus.data.clear();
     StockStatus.data.clear();
     PurchaseOrderStatus.data.clear();
+    SalesOrderStatus.data.clear();
+  }
+
+  Future<void> fetchStatusCodeData({bool forceReload = true}) async {
+    StockHistoryStatus.load(forceReload: forceReload);
+    StockStatus.load(forceReload: forceReload);
+    PurchaseOrderStatus.load(forceReload: forceReload);
+    SalesOrderStatus.load(forceReload: forceReload);
   }
 
   int notification_counter = 0;