Refactor server config models/commands

PluralKit.Core/Models/ModelQueryExt.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Data;
+using System.Threading.Tasks;
+
+using Dapper;
+
+namespace PluralKit.Core
+{
+    public static class ModelQueryExt
+    {
+        public static Task<GuildConfig> QueryOrInsertGuildConfig(this IDbConnection conn, ulong guild) =>
+            conn.QueryFirstOrDefaultAsync<GuildConfig>("insert into servers (id) values (@Guild) on conflict do nothing returning *", new {Guild = guild});
+    }
+}