Enable nullable annotations for Volo.Abp.Quartz

framework/src/Volo.Abp.Quartz/Volo.Abp.Quartz.csproj

@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Quartz</AssemblyName>
     <PackageId>Volo.Abp.Quartz</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>

framework/src/Volo.Abp.Quartz/Volo/Abp/Quartz/AbpQuartzModule.cs

@@ -10,7 +10,7 @@ namespace Volo.Abp.Quartz;
 
 public class AbpQuartzModule : AbpModule
 {
-    private IScheduler _scheduler;
+    private IScheduler _scheduler = default!;
 
     public override void ConfigureServices(ServiceConfigurationContext context)
     {

framework/src/Volo.Abp.Quartz/Volo/Abp/Quartz/AbpQuartzOptions.cs

@@ -13,7 +13,7 @@ public class AbpQuartzOptions
     /// </summary>
     public NameValueCollection Properties { get; set; }
 
-    public Action<IServiceCollectionQuartzConfigurator> Configurator { get; set; }
+    public Action<IServiceCollectionQuartzConfigurator>? Configurator { get; set; }
 
     /// <summary>
     /// How long Quartz should wait before starting. Default: 0.