Change exposed PropertyGroupType enum from int to string values

src/Umbraco.Core/Models/Mapping/ContentPropertyMapDefinition.cs

@@ -37,7 +37,7 @@ namespace Umbraco.Cms.Core.Models.Mapping
         {
             target.Id = source.Id;
             target.Key = source.Key;
-            target.Type = (int)source.Type;
+            target.Type = source.Type.ToString();
             target.Label = source.Name;
             target.Alias = source.Alias;
             target.IsActive = true;

src/Umbraco.Core/Models/Mapping/TabsAndPropertiesMapper.cs

@@ -158,7 +158,7 @@ namespace Umbraco.Cms.Core.Models.Mapping
                 {
                     Id = g.Id,
                     Key = g.Key,
-                    Type = (int)g.Type,
+                    Type = g.Type.ToString(),
                     Alias = g.Alias,
                     Label = LocalizedTextService.UmbracoDictionaryTranslate(CultureDictionary, g.Name),
                     Properties = mappedProperties