Use IUser instead of userid, add IGuild param to ToEntity

Replace ulong? user id of GuildEmote with Optional<IUser>.

Adds a util function in EntityExtensions for getting the emote
author, which requires the IGuild. Updates the GuildEmote
ToEntity extension to require an IGuild as a parameter.

Updates all instances of ToEntity to supply this IGuild parameter.

src/Discord.Net.Core/Entities/Emotes/GuildEmote.cs

@@ -31,19 +31,19 @@ namespace Discord
         /// </returns>
         public IReadOnlyList<ulong> RoleIds { get; }
         /// <summary>
-        ///     Gets the user Id that created this emoji.
+        ///     Gets the User that created this emoji.
         /// </summary>
         /// <returns>
-        ///     A user Id of the user who created this emoji, which may be null. A null value only indicates that the creator was not supplied as part of the API response.
-        /// </returns>
-        public ulong? CreatorId { get; }
+        ///     An optional <see cref="IUser"/> who created this emoji. An unspecified value only indicates that the creator was not supplied as part of the API response.
+        /// </returns>        
+        public Optional<IUser> Creator { get; }
 
-        internal GuildEmote(ulong id, string name, bool animated, bool isManaged, bool requireColons, IReadOnlyList<ulong> roleIds, ulong? userId) : base(id, name, animated)
+        internal GuildEmote(ulong id, string name, bool animated, bool isManaged, bool requireColons, IReadOnlyList<ulong> roleIds, Optional<IUser> creator) : base(id, name, animated)
         {
             IsManaged = isManaged;
             RequireColons = requireColons;
             RoleIds = roleIds;
-            CreatorId = userId;
+            Creator = creator;
         }
 
         private string DebuggerDisplay => $"{Name} ({Id})";

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -393,7 +393,7 @@ namespace Discord.Rest
         public static async Task<GuildEmote> GetEmoteAsync(IGuild guild, BaseDiscordClient client, ulong id, RequestOptions options)
         {
             var emote = await client.ApiClient.GetGuildEmoteAsync(guild.Id, id, options).ConfigureAwait(false);
-            return emote.ToEntity();
+            return emote.ToEntity(guild);
         }
         public static async Task<GuildEmote> CreateEmoteAsync(IGuild guild, BaseDiscordClient client, string name, Image image, Optional<IEnumerable<IRole>> roles, 
             RequestOptions options)
@@ -407,7 +407,7 @@ namespace Discord.Rest
                 apiargs.RoleIds = roles.Value?.Select(xr => xr.Id).ToArray();
 
             var emote = await client.ApiClient.CreateGuildEmoteAsync(guild.Id, apiargs, options).ConfigureAwait(false);
-            return emote.ToEntity();
+            return emote.ToEntity(guild);
         }
         /// <exception cref="ArgumentNullException"><paramref name="func"/> is <c>null</c>.</exception>
         public static async Task<GuildEmote> ModifyEmoteAsync(IGuild guild, BaseDiscordClient client, ulong id, Action<EmoteProperties> func, 
@@ -426,7 +426,7 @@ namespace Discord.Rest
                 apiargs.RoleIds = props.Roles.Value?.Select(xr => xr.Id).ToArray();
 
             var emote = await client.ApiClient.ModifyGuildEmoteAsync(guild.Id, id, apiargs, options).ConfigureAwait(false);
-            return emote.ToEntity();
+            return emote.ToEntity(guild);
         }
         public static Task DeleteEmoteAsync(IGuild guild, BaseDiscordClient client, ulong id, RequestOptions options) 
             => client.ApiClient.DeleteGuildEmoteAsync(guild.Id, id, options);

src/Discord.Net.Rest/Entities/Guilds/RestGuild.cs

@@ -109,7 +109,7 @@ namespace Discord.Rest
             {
                 var emotes = ImmutableArray.CreateBuilder<GuildEmote>(model.Emojis.Length);
                 for (int i = 0; i < model.Emojis.Length; i++)
-                    emotes.Add(model.Emojis[i].ToEntity());
+                    emotes.Add(model.Emojis[i].ToEntity(this));
                 _emotes = emotes.ToImmutableArray();
             }
             else

src/Discord.Net.Rest/Extensions/EntityExtensions.cs

@@ -5,9 +5,16 @@ namespace Discord.Rest
 {
     internal static class EntityExtensions
     {
-        public static GuildEmote ToEntity(this API.Emoji model)
+        public static GuildEmote ToEntity(this API.Emoji model, IGuild guild)
         {
-            return new GuildEmote(model.Id.Value, model.Name, model.Animated.GetValueOrDefault(), model.Managed, model.RequireColons, ImmutableArray.Create(model.Roles), model.User.IsSpecified ? model.User.Value.Id : (ulong?)null);
+            return new GuildEmote(model.Id.Value, model.Name, model.Animated.GetValueOrDefault(), model.Managed, model.RequireColons, ImmutableArray.Create(model.Roles), GetEmoteAuthor(model, guild));
+        }
+
+        internal static Optional<IUser> GetEmoteAuthor(API.Emoji model, IGuild guild)
+        {
+            if (!model.User.IsSpecified || guild == null)
+                return new Optional<IUser>();
+            return new Optional<IUser>(guild.GetUserAsync(model.User.Value.Id).Result);
         }
 
         public static Embed ToEntity(this API.Embed model)

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -359,7 +359,7 @@ namespace Discord.WebSocket
             {
                 var emojis = ImmutableArray.CreateBuilder<GuildEmote>(model.Emojis.Length);
                 for (int i = 0; i < model.Emojis.Length; i++)
-                    emojis.Add(model.Emojis[i].ToEntity());
+                    emojis.Add(model.Emojis[i].ToEntity(this));
                 _emotes = emojis.ToImmutable();
             }
             else
@@ -409,7 +409,7 @@ namespace Discord.WebSocket
         {
             var emotes = ImmutableArray.CreateBuilder<GuildEmote>(model.Emojis.Length);
             for (int i = 0; i < model.Emojis.Length; i++)
-                emotes.Add(model.Emojis[i].ToEntity());
+                emotes.Add(model.Emojis[i].ToEntity(this));
             _emotes = emotes.ToImmutable();
         }