feat: add error builder to options

This is done to allow for the user of this package to define custom error handling

packages/flutter_availability/lib/flutter_availability.dart

@@ -5,5 +5,6 @@ export "package:flutter_availability_data_interface/flutter_availability_data_in
 
 export "src/config/availability_options.dart";
 export "src/config/availability_translations.dart";
+export "src/service/errors.dart";
 export "src/ui/screens/availability_overview.dart";
 export "src/userstories.dart";

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

@@ -2,10 +2,12 @@ import "dart:async";
 
 import "package:flutter/material.dart";
 import "package:flutter_availability/src/config/availability_translations.dart";
+import "package:flutter_availability/src/service/errors.dart";
 import "package:flutter_availability/src/service/local_data_interface.dart";
 import "package:flutter_availability/src/ui/widgets/default_base_screen.dart";
 import "package:flutter_availability/src/ui/widgets/default_buttons.dart";
 import "package:flutter_availability/src/ui/widgets/default_confirmation_dialog.dart";
+import "package:flutter_availability/src/ui/widgets/default_error_display.dart";
 import "package:flutter_availability_data_interface/flutter_availability_data_interface.dart";
 
 /// Class that holds all options for the availability userstory
@@ -25,6 +27,7 @@ class AvailabilityOptions {
     this.confirmationDialogBuilder = DefaultConfirmationDialog.builder,
     this.timePickerBuilder,
     this.loadingIndicatorBuilder = DefaultLoader.builder,
+    this.errorDisplayBuilder = DefaultErrorDisplayDialog.defaultErrorDisplay,
     AvailabilityDataInterface? dataInterface,
   }) : dataInterface = dataInterface ?? LocalAvailabilityDataInterface();
 
@@ -82,6 +85,16 @@ class AvailabilityOptions {
   /// which shows a platform adaptive loading indicator
   final WidgetBuilder loadingIndicatorBuilder;
 
+  /// Builder for handling errors.
+  ///
+  /// The user should determine how to display the error, through a dialog,
+  /// popup or other method of user interaction.
+  ///
+  /// There is no guarantee that there is a scaffold in the tree for each of
+  /// the calls of the method. To ensure this, you can add a scaffold in the
+  /// base widget through [baseScreenBuilder].
+  final ErrorDisplayBuilder errorDisplayBuilder;
+
   final _borderRadius = BorderRadius.circular(5);
 
   /// The border radius used on the individual elements
@@ -204,6 +217,13 @@ typedef ConfirmationDialogBuilder = Future<bool> Function(
   required String description,
 });
 
+/// Typedef for the handler of any errors that occur during the usage of this
+/// userstory.
+typedef ErrorDisplayBuilder = Future<void> Function(
+  BuildContext context,
+  AvailabilityError error,
+);
+
 ///
 class DefaultLoader extends StatelessWidget {
   ///

packages/flutter_availability/lib/src/service/errors.dart

@@ -0,0 +1,12 @@
+/// A set of errors
+enum AvailabilityError {
+  /// Error identifier when checking break mismatch
+  breakMismatchWithAvailability(
+    "The break needs to be within the timeframe of the availability",
+  );
+
+  const AvailabilityError(this.description);
+
+  /// A more verbose description of the error.
+  final String description;
+}

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

@@ -0,0 +1,33 @@
+import "package:flutter/material.dart";
+import "package:flutter_availability/src/service/errors.dart";
+
+///
+class DefaultErrorDisplayDialog extends StatelessWidget {
+  ///
+  const DefaultErrorDisplayDialog({
+    required AvailabilityError error,
+    super.key,
+  }) : _error = error;
+
+  final AvailabilityError _error;
+
+  ///
+  static Future<void> defaultErrorDisplay(
+    BuildContext context,
+    AvailabilityError error,
+  ) async {
+    await showAdaptiveDialog(
+      context: context,
+      builder: (context) => DefaultErrorDisplayDialog(error: error),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) => Column(
+        children: [
+          Text(_error.name),
+          const SizedBox(height: 20),
+          Text(_error.description),
+        ],
+      );
+}