Audit Logs implementation (#1055)

* Copy audit logs impl from old branch and clean up

I suck at using git, so I'm gonna use brute force.

* Remove unnecessary TODOs

Category channels do not provide any new information, and the other
I forgot to remove beforehand

* Add invite update data, clean up after feedback

* Remove TODOs, add WebhookType enum for future use

WebhookType is a future-use type, as currently audit logs are the only
thing which may return it.

src/Discord.Net.Rest/Entities/AuditLogs/AuditLogHelper.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+
+using Model = Discord.API.AuditLog;
+using EntryModel = Discord.API.AuditLogEntry;
+
+namespace Discord.Rest
+{
+    internal static class AuditLogHelper
+    {
+        private static readonly Dictionary<ActionType, Func<BaseDiscordClient, Model, EntryModel, IAuditLogData>> CreateMapping
+            = new Dictionary<ActionType, Func<BaseDiscordClient, Model, EntryModel, IAuditLogData>>()
+        {
+            [ActionType.GuildUpdated] = GuildUpdateAuditLogData.Create,
+
+            [ActionType.ChannelCreated] = ChannelCreateAuditLogData.Create,
+            [ActionType.ChannelUpdated] = ChannelUpdateAuditLogData.Create,
+            [ActionType.ChannelDeleted] = ChannelDeleteAuditLogData.Create,
+
+            [ActionType.OverwriteCreated] = OverwriteCreateAuditLogData.Create,
+            [ActionType.OverwriteUpdated] = OverwriteUpdateAuditLogData.Create,
+            [ActionType.OverwriteDeleted] = OverwriteDeleteAuditLogData.Create,
+
+            [ActionType.Kick] = KickAuditLogData.Create,
+            [ActionType.Prune] = PruneAuditLogData.Create,
+            [ActionType.Ban] = BanAuditLogData.Create,
+            [ActionType.Unban] = UnbanAuditLogData.Create,
+            [ActionType.MemberUpdated] = MemberUpdateAuditLogData.Create,
+            [ActionType.MemberRoleUpdated] = MemberRoleAuditLogData.Create,
+
+            [ActionType.RoleCreated] = RoleCreateAuditLogData.Create,
+            [ActionType.RoleUpdated] = RoleUpdateAuditLogData.Create,
+            [ActionType.RoleDeleted] = RoleDeleteAuditLogData.Create,
+
+            [ActionType.InviteCreated] = InviteCreateAuditLogData.Create,
+            [ActionType.InviteUpdated] = InviteUpdateAuditLogData.Create,
+            [ActionType.InviteDeleted] = InviteDeleteAuditLogData.Create,
+
+            [ActionType.WebhookCreated] = WebhookCreateAuditLogData.Create,
+            [ActionType.WebhookUpdated] = WebhookUpdateAuditLogData.Create,
+            [ActionType.WebhookDeleted] = WebhookDeleteAuditLogData.Create,
+
+            [ActionType.EmojiCreated] = EmoteCreateAuditLogData.Create,
+            [ActionType.EmojiUpdated] = EmoteUpdateAuditLogData.Create,
+            [ActionType.EmojiDeleted] = EmoteDeleteAuditLogData.Create,
+
+            [ActionType.MessageDeleted] = MessageDeleteAuditLogData.Create,
+        };
+
+        public static IAuditLogData CreateData(BaseDiscordClient discord, Model log, EntryModel entry)
+        {
+            if (CreateMapping.TryGetValue(entry.Action, out var func))
+                return func(discord, log, entry);
+
+            return null;
+        }
+    }
+}