[9.1] Add WithExplicitStart (#2630)

* [9.1] Add WithExplicitStart

* Update docs/fundamentals/app-host-overview.md

Author: JamesNK

docs/fundamentals/app-host-overview.md

@@ -135,6 +135,25 @@ var apiservice = builder.AddProject<Projects.AspireApp_ApiService>("apiservice")
 
 The preceding code adds three replicas of the "apiservice" project resource to the app model. For more information, see [.NET Aspire dashboard: Resource replicas](dashboard/explore.md#resource-replicas).
 
+## Configure explicit resource start
+
+Project, executable and container resources are automatically started with your distributed application by default. A resource can be configured to wait for an explicit startup instruction with the `WithExplicitStart()` method. A resource configured with `WithExplicitStart()` is initialized with `KnownResourceStates.NotStarted`.
+
+```csharp
+var builder = DistributedApplication.CreateBuilder(args);
+
+var postgres = builder.AddPostgres("postgres");
+var postgresdb = postgres.AddDatabase("postgresdb");
+
+builder.AddProject<Projects.AspireApp_DbMigration>("dbmigration")
+       .WithReference(postgresdb)
+       .WithExplicitStart();
+```
+
+In the preceeding code the "dbmigration" resource is configured to not automatically start with the distributed application.
+
+Resources with explicit start can be started from the .NET Aspire dashboard by clicking the "Start" command. For more information, see [.NET Aspire dashboard: Stop or Start a resource](dashboard/explore#stop-or-start-a-resource).
+
 ## Reference resources
 
 A reference represents a dependency between resources. For example, you can probably imagine a scenario where you a web frontend depends on a Redis cache. Consider the following example app host `Program` C# code: