Make more types IDiscoverable

src/Umbraco.Core/Migrations/IPostMigration.cs

@@ -1,10 +1,11 @@
 using Semver;
+using Umbraco.Core.Composing;
 using Umbraco.Core.Logging;
 using Umbraco.Core.Scoping;
 
 namespace Umbraco.Core.Migrations
 {
-    public interface IPostMigration
+    public interface IPostMigration : IDiscoverable
     {
         void Execute(string name, IScope scope, SemVersion originVersion, SemVersion targetVersion, ILogger logger);
     }

src/Umbraco.Web/HealthCheck/NotificationMethods/IHealthCheckNotificationMethod.cs

@@ -1,9 +1,10 @@
 using System.Threading;
 using System.Threading.Tasks;
+using Umbraco.Core.Composing;
 
 namespace Umbraco.Web.HealthCheck.NotificationMethods
 {
-    public interface IHealthCheckNotificationMethod
+    public interface IHealthCheckNotificationMethod : IDiscoverable
     {
         bool Enabled { get; }
         Task SendAsync(HealthCheckResults results, CancellationToken token);