refactor: add SqlKata for SQL generation, move connection handling into ModelRepository

PluralKit.Core/Models/Patch/MemberGuildPatch.cs

@@ -1,4 +1,7 @@
 #nullable enable
+
+using SqlKata;
+
 namespace PluralKit.Core
 {
     public class MemberGuildPatch: PatchObject
@@ -6,8 +9,9 @@ namespace PluralKit.Core
         public Partial<string?> DisplayName { get; set; }
         public Partial<string?> AvatarUrl { get; set; }
 
-        public override UpdateQueryBuilder Apply(UpdateQueryBuilder b) => b
+        public override Query Apply(Query q) => q.ApplyPatch(wrapper => wrapper
             .With("display_name", DisplayName)
-            .With("avatar_url", AvatarUrl);
+            .With("avatar_url", AvatarUrl)
+        );
     }
 }