feat(Extensions): add Quartz job scheduling extension methods

- Introduced ScheduleJobDefault<TJob> extension for IServiceCollectionQuartzConfigurator
- Allows scheduling jobs using either a cron expression or configuration-based cron settings
- Includes validation for missing or invalid cron expressions

EnvelopeGenerator.Finalizer/Extensions.cs

@@ -0,0 +1,35 @@
+using EnvelopeGenerator.Finalizer.Job;
+using Quartz;
+
+namespace EnvelopeGenerator.Finalizer;
+
+public static class Extensions
+{
+    public static IServiceCollectionQuartzConfigurator ScheduleJobDefault<TJob>(this IServiceCollectionQuartzConfigurator q,
+        string croneEpression)
+        where TJob : IJob
+    {
+        var name = $"{typeof(TJob).FullName}";
+        var jobKey = new JobKey(name);
+
+        return q.ScheduleJob<TJob>(trigger => trigger
+            .WithIdentity(name + "-trigger")
+            .WithCronSchedule(croneEpression),
+            job => job.WithIdentity(jobKey)
+        );
+    }
+
+    public static IServiceCollectionQuartzConfigurator ScheduleJobDefault<TJob>(this IServiceCollectionQuartzConfigurator q,
+        IConfiguration configuration)
+        where TJob : IJob
+    {
+        var expression = configuration[$"{nameof(TJob)}:CronExpression"];
+        if (string.IsNullOrWhiteSpace(expression))
+            throw new InvalidOperationException(
+                "Cron expression for the Worker job is not configured. " +
+                "Please provide a valid cron schedule in the configuration under " +
+                $"'{nameof(TJob)}:CronExpression'.");
+
+        return q.ScheduleJobDefault<TJob>(expression);
+    }
+}