fix(controls): Prevent keyboard focus on hidden buttons in MessageBox (#1574)

Author: apachezy

src/Wpf.Ui/Controls/MessageBox/MessageBox.xaml

@@ -8,7 +8,10 @@
 <ResourceDictionary
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    xmlns:controls="clr-namespace:Wpf.Ui.Controls">
+    xmlns:controls="clr-namespace:Wpf.Ui.Controls"
+    xmlns:converters="clr-namespace:Wpf.Ui.Converters">
+
+    <converters:BoolToVisibilityConverter x:Key="BoolToVisibilityConverter" />
 
     <Style TargetType="{x:Type controls:MessageBox}">
         <Setter Property="MaxWidth" Value="450" />
@@ -109,7 +112,10 @@
                                             CommandParameter="{x:Static controls:MessageBoxButton.Primary}"
                                             Content="{TemplateBinding PrimaryButtonText}"
                                             Icon="{TemplateBinding PrimaryButtonIcon}"
-                                            IsDefault="True" />
+                                            IsDefault="True"
+                                            IsEnabled="{TemplateBinding IsPrimaryButtonEnabled}"
+                                            Visibility="{TemplateBinding IsPrimaryButtonEnabled,
+                                                                         Converter={StaticResource BoolToVisibilityConverter}}" />
 
                                         <controls:Button
                                             Grid.Column="2"
@@ -118,7 +124,10 @@
                                             Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type controls:MessageBox}}, Path=TemplateButtonCommand, Mode=OneTime}"
                                             CommandParameter="{x:Static controls:MessageBoxButton.Secondary}"
                                             Content="{TemplateBinding SecondaryButtonText}"
-                                            Icon="{TemplateBinding SecondaryButtonIcon}" />
+                                            Icon="{TemplateBinding SecondaryButtonIcon}"
+                                            IsEnabled="{TemplateBinding IsSecondaryButtonEnabled}"
+                                            Visibility="{TemplateBinding IsSecondaryButtonEnabled,
+                                                                         Converter={StaticResource BoolToVisibilityConverter}}" />
 
                                         <controls:Button
                                             Grid.Column="4"