Implemeted FlowFork activity (#4684)

src/modules/Elsa.Workflows.Core/Activities/Flowchart/Activities/FlowFork.cs

@@ -0,0 +1,37 @@
+using Elsa.Extensions;
+using Elsa.Workflows.Core.Attributes;
+using Elsa.Workflows.Core.Models;
+using JetBrains.Annotations;
+using System.Runtime.CompilerServices;
+
+namespace Elsa.Workflows.Core.Activities.Flowchart.Activities;
+
+/// <summary>
+/// Branch execution into multiple branches that will be executed in parallel.
+/// </summary>
+[Activity("Elsa", "Branching", "Branch execution into multiple branches that will be executed in parallel.", DisplayName = "Fork (flow)")]
+[PublicAPI]
+public class FlowFork : Activity
+{
+    /// <inheritdoc />
+    public FlowFork([CallerFilePath] string? source = default, [CallerLineNumber] int? line = default) : base(source, line)
+    {
+    }
+
+    /// <summary>
+    /// A list of expected outcomes to handle.
+    /// </summary>
+    [Input(
+        Description = "A list of expected outcomes to handle.",
+        UIHint = InputUIHints.DynamicOutcomes
+    )]
+    public Input<ICollection<string>> Branches { get; set; } = default!;
+
+    /// <inheritdoc />
+    protected override async ValueTask ExecuteAsync(ActivityExecutionContext context)
+    {
+        var outcomes = Branches.GetOrDefault(context)?.ToArray() ?? new[] { "Done" };
+
+        await context.ScheduleOutcomesAsync(outcomes);
+    }
+}