move SpoilerPrefix const outside of interface

src/Discord.Net.Core/Entities/Messages/IAttachment.cs

@@ -5,11 +5,6 @@ namespace Discord
     /// </summary>
     public interface IAttachment
     {
-        /// <summary>
-        ///     The prefix applied to files to indicate that it is a spoiler.
-        /// </summary>
-        public const string SpoilerPrefix = "SPOILER_";
-
         /// <summary>
         ///     Gets the ID of this attachment.
         /// </summary>

src/Discord.Net.Core/Extensions/AttachmentExtensions.cs

@@ -2,10 +2,14 @@ namespace Discord
 {
     public static class AttachmentExtensions
     {
+        /// <summary>
+        ///     The prefix applied to files to indicate that it is a spoiler.
+        /// </summary>
+        public const string SpoilerPrefix = "SPOILER_";
         /// <summary>
         ///     Gets whether the message's attachments are spoilers or not.
         /// </summary>
         public static bool IsSpoiler(this IAttachment attachment)
-            => attachment.Filename.StartsWith(IAttachment.SpoilerPrefix);
+            => attachment.Filename.StartsWith(SpoilerPrefix);
     }
 }

src/Discord.Net.Rest/API/Rest/UploadFileParams.cs

@@ -30,8 +30,8 @@ namespace Discord.API.Rest
         {
             var d = new Dictionary<string, object>();
             var filename = Filename.GetValueOrDefault("unknown.dat");
-            if (IsSpoiler && !filename.StartsWith(IAttachment.SpoilerPrefix))
-                filename = filename.Insert(0, IAttachment.SpoilerPrefix);
+            if (IsSpoiler && !filename.StartsWith(AttachmentExtensions.SpoilerPrefix))
+                filename = filename.Insert(0, AttachmentExtensions.SpoilerPrefix);
             d["file"] = new MultipartFile(File, filename);
 
             var payload = new Dictionary<string, object>();