Add project files.

src/common/Elsa.Features/Services/IFeature.cs

@@ -0,0 +1,31 @@
+using JetBrains.Annotations;
+
+namespace Elsa.Features.Services;
+
+/// <summary>
+/// Represents a feature.
+/// </summary>
+[UsedImplicitly(ImplicitUseTargetFlags.WithInheritors | ImplicitUseTargetFlags.Members)]
+public interface IFeature
+{
+    /// <summary>
+    /// Gets the module that this feature belongs to.
+    /// </summary>
+    IModule Module { get; }
+    
+    /// <summary>
+    /// Configures the feature.
+    /// </summary>
+    void Configure();
+    
+    /// <summary>
+    /// Configures the hosted services.
+    /// </summary>
+    void ConfigureHostedServices();
+    
+    /// <summary>
+    /// Applies the feature by adding services to the service collection.
+    /// </summary>
+    void Apply();
+    
+}