Adds language entity changes and tests

src/Umbraco.Core/Models/ILanguage.cs

@@ -23,5 +23,15 @@ namespace Umbraco.Core.Models
         /// </summary>
         [IgnoreDataMember]
         CultureInfo CultureInfo { get; }
+
+        /// <summary>
+        /// Defines if this language is the default variant language when language variants are in use
+        /// </summary>
+        bool IsDefaultVariantLanguage { get; set; }
+
+        /// <summary>
+        /// If true, a variant node cannot be published unless this language variant is created
+        /// </summary>
+        bool Mandatory { get; set; }
     }
 }