feat: add ScheduleType.Once and ScheduledAt for delayed one-off jobs

src/Trax.Effect.Data.Postgres/Migrations/023_once_schedule_type.sql

@@ -0,0 +1,18 @@
+-- Add 'once' value to schedule_type enum for one-off delayed jobs
+ALTER TYPE trax.schedule_type ADD VALUE IF NOT EXISTS 'once';
+
+-- Add scheduled_at column to manifest (used by Once schedule type)
+ALTER TABLE trax.manifest
+    ADD COLUMN IF NOT EXISTS scheduled_at timestamptz;
+
+-- Add scheduled_at column to work_queue (used by delayed triggers)
+ALTER TABLE trax.work_queue
+    ADD COLUMN IF NOT EXISTS scheduled_at timestamptz;
+
+-- Index for efficiently finding work queue entries with future scheduled_at.
+-- Note: no partial index on manifest for schedule_type='once' here because
+-- new enum values cannot be referenced in the same transaction they are added.
+-- The existing ix_manifest_scheduling index covers enabled manifests.
+CREATE INDEX IF NOT EXISTS ix_work_queue_scheduled_at
+    ON trax.work_queue (scheduled_at)
+    WHERE status = 'queued' AND scheduled_at IS NOT NULL;

src/Trax.Effect/Enums/ScheduleType.cs

@@ -80,4 +80,14 @@ public enum ScheduleType
     /// which dependents fire and with what input.
     /// </remarks>
     DormantDependent = 5,
+
+    /// <summary>
+    /// The manifest fires exactly once at a scheduled time, then auto-disables.
+    /// </summary>
+    /// <remarks>
+    /// Use this for delayed one-off jobs (e.g., "send reminder in 30 minutes").
+    /// The <see cref="Manifest.Manifest.ScheduledAt"/> property must be set.
+    /// After successful execution, the manifest is automatically disabled by the scheduler.
+    /// </remarks>
+    Once = 6,
 }

src/Trax.Effect/Models/Manifest/DTOs/CreateManifest.cs

@@ -70,5 +70,11 @@ public class CreateManifest
     /// </summary>
     public int? MisfireThresholdSeconds { get; set; }
 
+    /// <summary>
+    /// The earliest time this manifest should be executed.
+    /// Used with <see cref="ScheduleType.Once"/> for delayed one-off jobs.
+    /// </summary>
+    public DateTime? ScheduledAt { get; set; }
+
     #endregion
 }

src/Trax.Effect/Models/Manifest/Manifest.cs

@@ -173,6 +173,18 @@ public class Manifest : IModel
     [Column("misfire_threshold_seconds")]
     public int? MisfireThresholdSeconds { get; set; }
 
+    /// <summary>
+    /// Gets or sets the earliest time this manifest should be executed.
+    /// </summary>
+    /// <remarks>
+    /// Used with <see cref="ScheduleType.Once"/> to define when the one-off job should fire.
+    /// The ManifestManager will queue a work queue entry when <c>ScheduledAt &lt;= now</c>
+    /// and <see cref="LastSuccessfulRun"/> is null. After successful execution, the manifest
+    /// is automatically disabled.
+    /// </remarks>
+    [Column("scheduled_at")]
+    public DateTime? ScheduledAt { get; set; }
+
     #endregion
 
     #endregion
@@ -235,6 +247,7 @@ public static Manifest Create(CreateManifest manifest)
             Priority = manifest.Priority,
             MisfirePolicy = manifest.MisfirePolicy,
             MisfireThresholdSeconds = manifest.MisfireThresholdSeconds,
+            ScheduledAt = manifest.ScheduledAt,
         };
 
         if (manifest.Properties != null)

src/Trax.Effect/Models/WorkQueue/DTOs/CreateWorkQueue.cs

@@ -29,4 +29,10 @@ public class CreateWorkQueue
     /// Dispatch priority. Range: 0-31 (clamped in WorkQueue.Create). Defaults to 0.
     /// </summary>
     public int Priority { get; set; }
+
+    /// <summary>
+    /// The earliest time this work queue entry should be dispatched.
+    /// Null means dispatch immediately.
+    /// </summary>
+    public DateTime? ScheduledAt { get; set; }
 }

src/Trax.Effect/Models/WorkQueue/WorkQueue.cs

@@ -65,6 +65,17 @@
     [Column("dispatched_at")]
     public DateTime? DispatchedAt { get; set; }
 
+    /// <summary>
+    /// The earliest time this work queue entry should be dispatched.
+    /// </summary>
+    /// <remarks>
+    /// When set, the JobDispatcher will skip this entry until <c>ScheduledAt &lt;= now</c>.
+    /// Used by <c>TriggerAsync(externalId, delay)</c> to create delayed triggers without
+    /// affecting the manifest's normal schedule. Null means dispatch immediately.
+    /// </remarks>
+    [Column("scheduled_at")]
+    public DateTime? ScheduledAt { get; set; }
+
     /// <summary>
     /// Dispatch priority for this entry. Higher values (up to 31) are dispatched first.
     /// </summary>
@@ -114,6 +125,7 @@
             InputTypeName = dto.InputTypeName,
             ManifestId = dto.ManifestId,
             Priority = Math.Clamp(dto.Priority, MinPriority, MaxPriority),
+            ScheduledAt = dto.ScheduledAt,
             Status = WorkQueueStatus.Queued,
             CreatedAt = DateTime.UtcNow,
         };
@@ -129,5 +141,5 @@
     #endregion
 
     [JsonConstructor]
     public WorkQueue() { }
 }