Adding some initial work for Membership related classes and interfaces, but only using IProfile and Profile as the rest are not part of the roadmap.

Adding a UserService, which should be fully implemented in a later release.
Refactoring usage of the ServiceContext, which is now loosely tied to the HttpContext as its used by the UserService.
Refactoring User/Writer on the Content class and interface.
Simplifying events and delegates in the publishing strategy.

src/Umbraco.Core/Models/Membership/IMembershipUser.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Collections.Generic;
+
+namespace Umbraco.Core.Models.Membership
+{
+    internal interface IMembershipUser : IMembershipUserId
+    {
+        object Id { get; set; }
+        string Username { get; set; }
+        string Email { get; set; }
+        string Password { get; set; }
+        string PasswordQuestion { get; set; }
+        string PasswordAnswer { get; set; }
+        string Comments { get; set; }
+        bool IsApproved { get; set; }
+        bool IsOnline { get; set; }
+        bool IsLockedOut { get; set; }
+        DateTime CreationDate { get; set; }
+        DateTime LastLoginDate { get; set; }
+        DateTime LastActivityDate { get; set; }
+        DateTime LastPasswordChangeDate { get; set; }
+        DateTime LastLockoutDate { get; set; }
+
+        object ProfileId { get; set; }
+        IEnumerable<object> Groups { get; set; }
+    }
+}

src/Umbraco.Core/Models/Membership/IMembershipUserId.cs

@@ -0,0 +1,7 @@
+namespace Umbraco.Core.Models.Membership
+{
+    internal interface IMembershipUserId
+    {
+        object ProviderUserKey { get; set; }
+    }
+}

src/Umbraco.Core/Models/Membership/IProfile.cs

@@ -0,0 +1,11 @@
+namespace Umbraco.Core.Models.Membership
+{
+    /// <summary>
+    /// Defines the the Profile interface
+    /// </summary>
+    public interface IProfile
+    {
+        object Id { get; set; }
+        string Name { get; set; }
+    }
+}

src/Umbraco.Core/Models/Membership/Profile.cs

@@ -0,0 +1,52 @@
+using System;
+
+namespace Umbraco.Core.Models.Membership
+{
+    /// <summary>
+    /// Represents a Profile which is shared between Members and Users
+    /// </summary>
+    public class Profile : IProfile
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Profile"/> class.
+        /// </summary>
+        public Profile()
+        {
+            ProviderUserKeyType = typeof(int);
+        }
+
+        public Profile(object id, string name)
+        {
+            ProviderUserKeyType = typeof(int);
+            Id = id;
+            Name = name;
+        }
+
+        public object Id { get; set; }
+
+        public string Name { get; set; }
+
+        internal virtual object ProviderUserKey
+        {
+            get { throw new System.NotImplementedException(); }
+            set { throw new System.NotImplementedException(); }
+        }
+
+        /// <summary>
+        /// Gets or sets the type of the provider user key.
+        /// </summary>
+        /// <value>
+        /// The type of the provider user key.
+        /// </value>
+        internal Type ProviderUserKeyType { get; private set; }
+
+        /// <summary>
+        /// Sets the type of the provider user key.
+        /// </summary>
+        /// <param name="type">The type.</param>
+        internal void SetProviderUserKeyType(Type type)
+        {
+            ProviderUserKeyType = type;
+        }
+    }
+}

src/Umbraco.Core/Models/Membership/User.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+
+namespace Umbraco.Core.Models.Membership
+{
+    /// <summary>
+    /// Represents a backoffice user
+    /// </summary>
+    /// <remarks>
+    /// Should be internal until a proper user/membership implementation
+    /// is part of the roadmap.
+    /// </remarks>
+    internal class User : UserProfile, IMembershipUser
+    {
+        #region Implementation of IMembershipUser
+
+        public string Username { get; set; }
+        public string Email { get; set; }
+        public string Password { get; set; }
+        public string PasswordQuestion { get; set; }
+        public string PasswordAnswer { get; set; }
+        public string Comments { get; set; }
+        public bool IsApproved { get; set; }
+        public bool IsOnline { get; set; }
+        public bool IsLockedOut { get; set; }
+        public DateTime CreationDate { get; set; }
+        public DateTime LastLoginDate { get; set; }
+        public DateTime LastActivityDate { get; set; }
+        public DateTime LastPasswordChangeDate { get; set; }
+        public DateTime LastLockoutDate { get; set; }
+
+        public object ProfileId { get; set; }
+        public IEnumerable<object> Groups { get; set; }
+
+        #endregion
+
+        #region Implementation of IMembershipUserId
+
+        public new object ProviderUserKey { get; set; }
+
+        #endregion
+    }
+}

src/Umbraco.Core/Models/Membership/UserProfile.cs

@@ -0,0 +1,53 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Umbraco.Core.Models.Membership
+{
+    /// <summary>
+    /// Represents the Profile implementation for a backoffice User
+    /// </summary>
+    /// <remarks>
+    /// Should be internal until a proper user/membership implementation
+    /// is part of the roadmap.
+    /// </remarks>
+    internal class UserProfile : Profile
+    {
+        public UserProfile()
+        {
+            SessionTimeout = 60;
+            Applications = Enumerable.Empty<string>();
+        }
+
+        /// <summary>
+        /// Gets or sets the session timeout.
+        /// </summary>
+        /// <value>
+        /// The session timeout.
+        /// </value>
+        public int SessionTimeout { get; set; }
+
+        /// <summary>
+        /// Gets or sets the start content id.
+        /// </summary>
+        /// <value>
+        /// The start content id.
+        /// </value>
+        public int StartContentId { get; set; }
+
+        /// <summary>
+        /// Gets or sets the start media id.
+        /// </summary>
+        /// <value>
+        /// The start media id.
+        /// </value>
+        public int StartMediaId { get; set; }
+
+        /// <summary>
+        /// Gets or sets the applications.
+        /// </summary>
+        /// <value>
+        /// The applications.
+        /// </value>
+        public IEnumerable<string> Applications { get; set; }
+    }
+}