Added two further notifications to the boot process for custom functionality that may need to run at different stages. (#10471)

src/Umbraco.Core/Notifications/UmbracoApplicationComponentsInstallingNotification.cs

@@ -0,0 +1,22 @@
+// Copyright (c) Umbraco.
+// See LICENSE for more details.
+
+namespace Umbraco.Cms.Core.Notifications
+{
+    /// <summary>
+    /// Notification that occurs during the Umbraco boot process, before instances of <see cref="IComponent"/> initialize.
+    /// </summary>
+    public class UmbracoApplicationComponentsInstallingNotification : INotification
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UmbracoApplicationStartingNotification"/> class.
+        /// </summary>
+        /// <param name="runtimeLevel">The runtime level</param>
+        public UmbracoApplicationComponentsInstallingNotification(RuntimeLevel runtimeLevel) => RuntimeLevel = runtimeLevel;
+
+        /// <summary>
+        /// Gets the runtime level of execution.
+        /// </summary>
+        public RuntimeLevel RuntimeLevel { get; }
+    }
+}

src/Umbraco.Core/Notifications/UmbracoApplicationMainDomAcquiredNotification.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Umbraco.
+// See LICENSE for more details.
+
+namespace Umbraco.Cms.Core.Notifications
+{
+    /// <summary>
+    /// Notification that occurs during Umbraco boot after the MainDom has been acquired.
+    /// </summary>
+    public class UmbracoApplicationMainDomAcquiredNotification : INotification
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UmbracoApplicationMainDomAcquiredNotification"/> class.
+        /// </summary>
+        /// <param name="runtimeLevel">The runtime level</param>
+        public UmbracoApplicationMainDomAcquiredNotification()
+        {
+        }
+    }
+}