feat(apiv2): database changes

PluralKit.Core/Database/Repository/ModelRepository.Group.cs

@@ -1,4 +1,5 @@
 #nullable enable
+using System;
 using System.Collections.Generic;
 using System.Data;
 using System.Linq;
@@ -23,6 +24,9 @@ namespace PluralKit.Core
                 new { hid = hid.ToLowerInvariant(), System = system }
             );
 
+        public Task<PKGroup?> GetGroupByGuid(IPKConnection conn, Guid guid) =>
+            conn.QueryFirstOrDefaultAsync<PKGroup?>("select * from groups where uuid = @Uuid", new { Uuid = guid });
+
         public Task<int> GetGroupMemberCount(IPKConnection conn, GroupId id, PrivacyLevel? privacyFilter = null)
         {
             var query = new StringBuilder("select count(*) from group_members");