feat: add loadingIndicatorBuilder to override CircularProgressIndicator.adaptive()

packages/flutter_availability/lib/src/config/availability_options.dart

@@ -19,6 +19,7 @@ class AvailabilityOptions {
     this.textStyles = const AvailabilityTextStyles(),
     this.colors = const AvailabilityColors(),
     this.timePickerBuilder,
+    this.loadingIndicatorBuilder = defaultLoader,
     AvailabilityDataInterface? dataInterface,
   }) : dataInterface = dataInterface ?? LocalAvailabilityDataInterface();
 
@@ -53,6 +54,11 @@ class AvailabilityOptions {
   /// A way to provide your own time picker implementation or customize
   /// the default time picker
   final TimePickerBuilder? timePickerBuilder;
+
+  /// A builder to override the loading indicator
+  /// If not provided the [CircularProgressIndicator.adaptive()] will be used
+  /// which shows a platform adaptive loading indicator
+  final WidgetBuilder loadingIndicatorBuilder;
 }
 
 /// All configurable paddings and whitespaces withing the userstory
@@ -154,3 +160,9 @@ typedef TimePickerBuilder = Future<TimeOfDay?> Function(
   BuildContext context,
   TimeOfDay? initialTime,
 );
+
+/// Builder definition for providing a loading indicator implementation
+Widget defaultLoader(
+  BuildContext context,
+) =>
+    const CircularProgressIndicator.adaptive();

packages/flutter_availability/lib/src/ui/screens/template_overview.dart

@@ -101,6 +101,8 @@ class _TemplateListSection extends StatelessWidget {
   Widget build(BuildContext context) {
     var theme = Theme.of(context);
     var textTheme = theme.textTheme;
+    var availabilityScope = AvailabilityScope.of(context);
+    var options = availabilityScope.options;
 
     var templateCreationButton = GestureDetector(
       onTap: onAddTemplate,
@@ -160,7 +162,7 @@ class _TemplateListSection extends StatelessWidget {
           ),
         ],
         if (templatesSnapshot.connectionState == ConnectionState.waiting) ...[
-          const Center(child: CircularProgressIndicator.adaptive()),
+          Center(child: options.loadingIndicatorBuilder(context)),
         ],
         const SizedBox(height: 8),
         templateCreationButton,

packages/flutter_availability/lib/src/ui/widgets/template_legend.dart

@@ -179,7 +179,7 @@ class _TemplateLegendState extends State<TemplateLegend> {
             (!_templateDrawerOpen || templatesLoading)) ...[
           const SizedBox(height: 12),
           if (templatesLoading) ...[
-            const CircularProgressIndicator.adaptive(),
+            options.loadingIndicatorBuilder(context),
           ] else ...[
             createNewTemplateButton,
           ],