Merge remote-tracking branch 'origin/v9/dev' into v9/task/package-refactor

# Conflicts:
#	src/Umbraco.Core/Migrations/IMigration.cs
#	src/Umbraco.Core/Migrations/MigrationPlan.cs
#	src/Umbraco.Infrastructure/Migrations/IMigrationContext.cs
#	src/Umbraco.Infrastructure/Runtime/RuntimeState.cs
#	src/Umbraco.Tests.UnitTests/Umbraco.Infrastructure/Migrations/MigrationTests.cs
#	src/Umbraco.Web.UI.NetCore/umbraco/config/lang/en.xml
#	src/Umbraco.Web.UI.NetCore/umbraco/config/lang/en_us.xml

src/Umbraco.Core/Models/IContentBase.cs

@@ -4,6 +4,7 @@ using Umbraco.Cms.Core.Models.Entities;
 
 namespace Umbraco.Cms.Core.Models
 {
+
     /// <summary>
     /// Provides a base class for content items.
     /// </summary>

src/Umbraco.Core/Models/IReadOnlyContentBase.cs

@@ -0,0 +1,72 @@
+using System;
+
+namespace Umbraco.Cms.Core.Models
+{
+    public interface IReadOnlyContentBase
+    {
+        /// <summary>
+        /// Gets the integer identifier of the entity.
+        /// </summary>
+        int Id { get; }
+
+        /// <summary>
+        /// Gets the Guid unique identifier of the entity.
+        /// </summary>
+        Guid Key { get; }
+
+        /// <summary>
+        /// Gets the creation date.
+        /// </summary>
+        DateTime CreateDate { get; }
+
+        /// <summary>
+        /// Gets the last update date.
+        /// </summary>
+        DateTime UpdateDate { get; }
+
+        /// <summary>
+        /// Gets the name of the entity.
+        /// </summary>
+        string Name { get; }
+
+        /// <summary>
+        /// Gets the identifier of the user who created this entity.
+        /// </summary>
+        int CreatorId { get; }
+
+        /// <summary>
+        /// Gets the identifier of the parent entity.
+        /// </summary>
+        int ParentId { get; }
+
+        /// <summary>
+        /// Gets the level of the entity.
+        /// </summary>
+        int Level { get; }
+
+        /// <summary>
+        /// Gets the path to the entity.
+        /// </summary>
+        string Path { get; }
+
+        /// <summary>
+        /// Gets the sort order of the entity.
+        /// </summary>
+        int SortOrder { get; }
+
+        /// <summary>
+        /// Gets the content type id
+        /// </summary>
+        int ContentTypeId { get; }
+
+        /// <summary>
+        /// Gets the identifier of the writer.
+        /// </summary>
+        int WriterId { get; }
+
+        /// <summary>
+        /// Gets the version identifier.
+        /// </summary>
+        int VersionId { get; }
+    }
+}

src/Umbraco.Core/Models/ReadOnlyContentBaseAdapter.cs

@@ -0,0 +1,42 @@
+using System;
+
+namespace Umbraco.Cms.Core.Models
+{
+    public struct ReadOnlyContentBaseAdapter : IReadOnlyContentBase
+    {
+        private readonly IContentBase _content;
+
+        private ReadOnlyContentBaseAdapter(IContentBase content)
+        {
+            _content = content ?? throw new ArgumentNullException(nameof(content));
+        }
+
+        public static ReadOnlyContentBaseAdapter Create(IContentBase content) => new ReadOnlyContentBaseAdapter(content);
+
+        public int Id => _content.Id;
+
+        public Guid Key => _content.Key;
+
+        public DateTime CreateDate => _content.CreateDate;
+
+        public DateTime UpdateDate => _content.UpdateDate;
+
+        public string Name => _content.Name;
+
+        public int CreatorId => _content.CreatorId;
+
+        public int ParentId => _content.ParentId;
+
+        public int Level => _content.Level;
+
+        public string Path => _content.Path;
+
+        public int SortOrder => _content.SortOrder;
+
+        public int ContentTypeId => _content.ContentTypeId;
+
+        public int WriterId => _content.WriterId;
+
+        public int VersionId => _content.VersionId;
+    }
+}