Modern Label printing (#724)

* Basic widget

* Redirect label printing action

* Refactor label printing code

* Construct form elements

* Refactor to allow re-use of forms

* Basic rendering of label printing form

* Remove dead code

* Pass custom handler through to form context

* Refactoring API forms:

- Allow custom pk field name
- Add callback when values change

* linting

* Dynamically rebuild form

* Handle nested fields

* Handle label printing status

* Run dart format

* Update release notes

* Remove unused var

* Enable close icon

* Handle initial plugin default value

* Store default values:

- Selected template (per label type)
- Selected printing plugin

* Dart format

* Fix dart linting

* use setter

* Just use a public field

lib/widget/stock/stock_detail.dart

@@ -128,19 +128,13 @@ class _StockItemDisplayState extends RefreshableState<StockDetailWidget> {
       );
     }
 
-    if (labels.isNotEmpty) {
+    if (allowLabelPrinting && api.supportsModernLabelPrinting) {
       actions.add(
         SpeedDialChild(
           child: Icon(TablerIcons.printer),
           label: L10().printLabel,
           onTap: () async {
-            selectAndPrintLabel(
-              context,
-              labels,
-              widget.item.pk,
-              "stock",
-              "item=${widget.item.pk}",
-            );
+            selectAndPrintLabel(context, "stockitem", widget.item.pk);
           },
         ),
       );
@@ -196,10 +190,7 @@ class _StockItemDisplayState extends RefreshableState<StockDetailWidget> {
     return actions;
   }
 
-  // Is label printing enabled for this StockItem?
-  // This will be determined when the widget is loaded
-  List<Map<String, dynamic>> labels = [];
-
+  bool allowLabelPrinting = false;
   int attachmentCount = 0;
 
   @override
@@ -318,31 +309,10 @@ class _StockItemDisplayState extends RefreshableState<StockDetailWidget> {
       }
     }
 
-    List<Map<String, dynamic>> _labels = [];
-    bool allowLabelPrinting = await InvenTreeSettingsManager().getBool(
+    allowLabelPrinting = await InvenTreeSettingsManager().getBool(
       INV_ENABLE_LABEL_PRINTING,
       true,
     );
-    allowLabelPrinting &= api.supportsMixin("labels");
-
-    // Request information on labels available for this stock item
-    if (allowLabelPrinting) {
-      String model_type = api.supportsModernLabelPrinting
-          ? InvenTreeStockItem.MODEL_TYPE
-          : "stock";
-      String item_key = api.supportsModernLabelPrinting ? "items" : "item";
-
-      // Clear the existing labels list
-      _labels = await getLabelTemplates(model_type, {
-        item_key: widget.item.pk.toString(),
-      });
-    }
-
-    if (mounted) {
-      setState(() {
-        labels = _labels;
-      });
-    }
   }
 
   /// Delete the stock item from the database