The default text style for the AppBar's leading, and actions widgets, but not its title.
If this property is null, then AppBarTheme.toolbarTextStyle of ThemeData.appBarTheme is used. If that is also null, the default value is a copy of the overall theme's TextTheme.bodyMedium TextStyle, with color set to the app bar's foregroundColor.
This property is used to configure an AppBar.
final TextStyle? toolbarTextStyle;