Explicitly set default value for enums used in API models (#13821)

Enums in response model with no nullability or default value will make the API very fragile as each extension to the enum will break the API for some clients, but a lot of enums actually do have an unknown value which should be used as a default. This set all model properties that are non-nullable using an enum that has an Unknown member in 10.10, except MediaStream.VideoRangeType which is refactored in #13277

MediaBrowser.Model/MediaSegments/MediaSegmentDto.cs

@@ -1,4 +1,5 @@
 using System;
+using System.ComponentModel;
 using Jellyfin.Database.Implementations.Enums;
 
 namespace MediaBrowser.Model.MediaSegments;
@@ -21,6 +22,7 @@ public class MediaSegmentDto
     /// <summary>
     /// Gets or sets the type of content this segment defines.
     /// </summary>
+    [DefaultValue(MediaSegmentType.Unknown)]
     public MediaSegmentType Type { get; set; }
 
     /// <summary>