Make notes widget "generic" (#327)

* Make notes widget "generic"

- No longer tied to the "part" model
- Will allow us to use it elsewhere

* Update release notes

* Add helper methods for checking model permissions

* Refactoring of permissions checks

* Add notes to the "purchase order" widget

* Fix typos

* remove bom tab from part view

* linting fixes

lib/inventree/company.dart

@@ -18,6 +18,9 @@ class InvenTreeCompany extends InvenTreeModel {
   @override
   String get URL => "company/";
 
+  @override
+  List<String> get rolesRequired => ["purchase_order", "sales_order", "return_order"];
+
   @override
   Map<String, dynamic> formFields() {
     return {
@@ -118,6 +121,9 @@ class InvenTreeSupplierPart extends InvenTreeModel {
   @override
   String get URL => "company/part/";
 
+  @override
+  List<String> get rolesRequired => ["part", "purchase_order"];
+
   @override
   Map<String, dynamic> formFields() {
     return {

lib/inventree/model.dart

@@ -10,6 +10,7 @@ import "package:inventree/api.dart";
 import "package:inventree/api_form.dart";
 import "package:inventree/fa_icon_mapping.dart";
 import "package:inventree/l10.dart";
+import "package:inventree/helpers.dart";
 import "package:inventree/inventree/sentry.dart";
 import "package:inventree/widget/dialogs.dart";
 
@@ -78,7 +79,63 @@ class InvenTreeModel {
     } else {
       return "";
     }
+  }
 
+  /* Return a list of roles which may be required for this model
+   * If multiple roles are required, *any* role which passes the check is sufficient
+   */
+  List<String> get rolesRequired {
+    // Default implementation should not be called
+    debug("rolesRequired() not implemented for model ${URL} - returning empty list");
+    return [];
+  }
+
+  // Test if the user can "edit" this model
+  bool get canEdit {
+    for (String role in rolesRequired) {
+      if (InvenTreeAPI().checkPermission(role, "change")) {
+        return true;
+      }
+    }
+
+    // Fallback
+    return false;
+  }
+
+  // Test if the user can "create" this model
+  bool get canCreate {
+    for (String role in rolesRequired) {
+      if (InvenTreeAPI().checkPermission(role, "add")) {
+        return true;
+      }
+    }
+
+    // Fallback
+    return false;
+  }
+
+  // Test if the user can "delete" this model
+  bool get canDelete {
+    for (String role in rolesRequired) {
+      if (InvenTreeAPI().checkPermission(role, "delete")) {
+        return true;
+      }
+    }
+
+    // Fallback
+    return false;
+  }
+
+  // Test if the user can "view" this model
+  bool get canView {
+    for (String role in rolesRequired) {
+      if (InvenTreeAPI().checkPermission(role, "view")) {
+        return true;
+      }
+    }
+
+    // Fallback
+    return false;
   }
 
   // Fields for editing / creating this model

lib/inventree/part.dart

@@ -23,6 +23,9 @@ class InvenTreePartCategory extends InvenTreeModel {
   @override
   String get URL => "part/category/";
 
+  @override
+  List<String> get rolesRequired => ["part_category"];
+
   @override
   Map<String, dynamic> formFields() {
 
@@ -182,6 +185,9 @@ class InvenTreePart extends InvenTreeModel {
   @override
   String get URL => "part/";
 
+  @override
+  List<String> get rolesRequired => ["part"];
+
   @override
   Map<String, dynamic> formFields() {
     return {

lib/inventree/purchase_order.dart

@@ -18,6 +18,9 @@ class InvenTreePurchaseOrder extends InvenTreeModel {
   @override
   String get URL => "order/po/";
 
+  @override
+  List<String> get rolesRequired => ["purchase_order"];
+
   String get receive_url => "${url}receive/";
 
   @override

lib/inventree/stock.dart

@@ -20,6 +20,9 @@ class InvenTreeStockItemTestResult extends InvenTreeModel {
   @override
   String get URL => "stock/test/";
 
+  @override
+  List<String> get rolesRequired => ["stock"];
+
   @override
   Map<String, dynamic> formFields() {
     return {
@@ -134,6 +137,9 @@ class InvenTreeStockItem extends InvenTreeModel {
   @override
   String get URL => "stock/";
 
+  @override
+  List<String> get rolesRequired => ["stock"];
+
   // URLs for performing stock actions
   static String transferStockUrl() => "stock/transfer/";
 
@@ -611,6 +617,9 @@ class InvenTreeStockLocation extends InvenTreeModel {
   @override
   String get URL => "stock/location/";
 
+  @override
+  List<String> get rolesRequired => ["stock_location"];
+
   String get pathstring => (jsondata["pathstring"] ?? "") as String;
 
   @override