IsImmutable weird behaviour

[wisepotato]

Lets say I have the following model

using Tbdc.Apis.Mgmt.Authorization;
using Tbdc.Apis.Mgmt.Models.Authorization;
using JsonApiDotNetCore.Models;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;
using Bdc.Api.Management.Models;
using Bdc.Api.Management.Models.Contracts;
using Bdc.Api.Management.Models.Abstract;

namespace Tbdc.Apis.Mgmt.Models
{
    /// <summary>
    /// The user model
    /// </summary>
    public class User :  Identifiable, ITraversable
    {
        [HasMany("cachedReports", canInclude: false), NotMapped]
        public List<Report> CachedReports { get; set; }
        [Attr("firstName", isImmutable: true)]
        public string FirstName { get; set; }

        [Attr("tussenvoegsel", isImmutable: true)]
        public string Tussenvoegsel { get; set; }

        [Attr("fullName", isImmutable: true)]
        public string FullName
        {
            get => this.FirstName + (this.Tussenvoegsel != null ? " " + this.Tussenvoegsel : "") + " " + this.LastName;
        }
        [Attr("lastName", isImmutable: true)]
        public string LastName { get; set; }
    }
}

If I deserialize something coming in that has fullName I dont want it to be set.

Environment

• JsonApiDotNetCore Version:
• Other Relevant Package Versions:

[milosloub]

Can you set fullName if it is read-only? (only get accessor)