Merge remote-tracking branch 'origin/v10/dev' into v10/feature/nullable-reference-types-in-Umbraco-Core

# Conflicts:
#	src/Umbraco.Core/Configuration/Models/SecuritySettings.cs
#	src/Umbraco.Core/Events/DeleteEventArgs.cs
#	src/Umbraco.Core/Events/IEventDispatcher.cs
#	src/Umbraco.Core/Events/PassThroughEventDispatcher.cs
#	src/Umbraco.Core/Events/QueuingEventDispatcherBase.cs
#	src/Umbraco.Core/IO/MediaFileManager.cs
#	src/Umbraco.Core/Models/Mapping/MemberTabsAndPropertiesMapper.cs
#	src/Umbraco.Core/PropertyEditors/DataValueEditor.cs
#	src/Umbraco.Core/Routing/DefaultUrlProvider.cs

src/Umbraco.Core/Notifications/IUmbracoApplicationLifetimeNotification.cs

@@ -0,0 +1,17 @@
+namespace Umbraco.Cms.Core.Notifications
+{
+    /// <summary>
+    /// Represents an Umbraco application lifetime (starting, started, stopping, stopped) notification.
+    /// </summary>
+    /// <seealso cref="Umbraco.Cms.Core.Notifications.INotification" />
+    public interface IUmbracoApplicationLifetimeNotification : INotification
+    {
+        /// <summary>
+        /// Gets a value indicating whether Umbraco is restarting (e.g. after an install or upgrade).
+        /// </summary>
+        /// <value>
+        ///   <c>true</c> if Umbraco is restarting; otherwise, <c>false</c>.
+        /// </value>
+        bool IsRestarting { get; }
+    }
+}

src/Umbraco.Core/Notifications/MemberTwoFactorRequestedNotification.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace Umbraco.Cms.Core.Notifications
+{
+    public class MemberTwoFactorRequestedNotification : INotification
+    {
+        public MemberTwoFactorRequestedNotification(Guid memberKey)
+        {
+            MemberKey = memberKey;
+        }
+
+        public Guid MemberKey { get; }
+    }
+}

src/Umbraco.Core/Notifications/UmbracoApplicationStartedNotification.cs

@@ -0,0 +1,18 @@
+namespace Umbraco.Cms.Core.Notifications
+{
+    /// <summary>
+    /// Notification that occurs when Umbraco has completely booted up and the request processing pipeline is configured.
+    /// </summary>
+    /// <seealso cref="Umbraco.Cms.Core.Notifications.IUmbracoApplicationLifetimeNotification" />
+    public class UmbracoApplicationStartedNotification : IUmbracoApplicationLifetimeNotification
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UmbracoApplicationStartedNotification" /> class.
+        /// </summary>
+        /// <param name="isRestarting">Indicates whether Umbraco is restarting.</param>
+        public UmbracoApplicationStartedNotification(bool isRestarting) => IsRestarting = isRestarting;
+
+        /// <inheritdoc />
+        public bool IsRestarting { get; }
+    }
+}

src/Umbraco.Core/Notifications/UmbracoApplicationStartingNotification.cs

@@ -1,23 +1,44 @@
-// Copyright (c) Umbraco.
-// See LICENSE for more details.
+using System;
 
 namespace Umbraco.Cms.Core.Notifications
 {
     /// <summary>
-    /// Notification that occurs at the very end of the Umbraco boot
-    /// process and after all <see cref="IComponent"/> initialize.
+    /// Notification that occurs at the very end of the Umbraco boot process (after all <see cref="IComponent" />s are initialized).
     /// </summary>
-    public class UmbracoApplicationStartingNotification : INotification
+    /// <seealso cref="Umbraco.Cms.Core.Notifications.IUmbracoApplicationLifetimeNotification" />
+    public class UmbracoApplicationStartingNotification : IUmbracoApplicationLifetimeNotification
     {
         /// <summary>
-        /// Initializes a new instance of the <see cref="UmbracoApplicationStartingNotification"/> class.
+        /// Initializes a new instance of the <see cref="UmbracoApplicationStartingNotification" /> class.
         /// </summary>
         /// <param name="runtimeLevel">The runtime level</param>
-        public UmbracoApplicationStartingNotification(RuntimeLevel runtimeLevel) => RuntimeLevel = runtimeLevel;
+        [Obsolete("Use ctor with all params")]
+        public UmbracoApplicationStartingNotification(RuntimeLevel runtimeLevel)
+            : this(runtimeLevel, false)
+        {
+            // TODO: Remove this constructor in V10
+        }
 
         /// <summary>
-        /// Gets the runtime level of execution.
+        /// Initializes a new instance of the <see cref="UmbracoApplicationStartingNotification" /> class.
         /// </summary>
+        /// <param name="runtimeLevel">The runtime level</param>
+        /// <param name="isRestarting">Indicates whether Umbraco is restarting.</param>
+        public UmbracoApplicationStartingNotification(RuntimeLevel runtimeLevel, bool isRestarting)
+        {
+            RuntimeLevel = runtimeLevel;
+            IsRestarting = isRestarting;
+        }
+
+        /// <summary>
+        /// Gets the runtime level.
+        /// </summary>
+        /// <value>
+        /// The runtime level.
+        /// </value>
         public RuntimeLevel RuntimeLevel { get; }
+
+        /// <inheritdoc />
+        public bool IsRestarting { get; }
     }
 }

src/Umbraco.Core/Notifications/UmbracoApplicationStoppedNotification.cs

@@ -0,0 +1,18 @@
+namespace Umbraco.Cms.Core.Notifications
+{
+    /// <summary>
+    /// Notification that occurs when Umbraco has completely shutdown.
+    /// </summary>
+    /// <seealso cref="Umbraco.Cms.Core.Notifications.IUmbracoApplicationLifetimeNotification" />
+    public class UmbracoApplicationStoppedNotification : IUmbracoApplicationLifetimeNotification
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UmbracoApplicationStoppedNotification" /> class.
+        /// </summary>
+        /// <param name="isRestarting">Indicates whether Umbraco is restarting.</param>
+        public UmbracoApplicationStoppedNotification(bool isRestarting) => IsRestarting = isRestarting;
+
+        /// <inheritdoc />
+        public bool IsRestarting { get; }
+    }
+}

src/Umbraco.Core/Notifications/UmbracoApplicationStoppingNotification.cs

@@ -1,4 +1,30 @@
+using System;
+
 namespace Umbraco.Cms.Core.Notifications
 {
-    public class UmbracoApplicationStoppingNotification : INotification { }
+    /// <summary>
+    /// Notification that occurs when Umbraco is shutting down (after all <see cref="IComponent" />s are terminated).
+    /// </summary>
+    /// <seealso cref="Umbraco.Cms.Core.Notifications.IUmbracoApplicationLifetimeNotification" />
+    public class UmbracoApplicationStoppingNotification : IUmbracoApplicationLifetimeNotification
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UmbracoApplicationStoppingNotification" /> class.
+        /// </summary>
+        [Obsolete("Use ctor with all params")]
+        public UmbracoApplicationStoppingNotification()
+            : this(false)
+        {
+            // TODO: Remove this constructor in V10
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UmbracoApplicationStoppingNotification" /> class.
+        /// </summary>
+        /// <param name="isRestarting">Indicates whether Umbraco is restarting.</param>
+        public UmbracoApplicationStoppingNotification(bool isRestarting) => IsRestarting = isRestarting;
+
+        /// <inheritdoc />
+        public bool IsRestarting { get; }
+    }
 }