[Column("UserId")]
    public string UserId { get; set; } = null!; // this one

    [ForeignKey(nameof(UserId))]
    public virtual ApplicationUser? User { get; set; }

    [Column("UserId")]
    public string UserId { get; set; } = null!; // this one

    [ForeignKey(nameof(UserId))]
    public virtual ApplicationUser? User { get; set; }

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<IdeaViewModel>()
        .HasOne(i => i.User)
        .WithMany()
        .HasForeignKey("UserId")
        .HasConstraintName("FK_IdeaViewModel_User");

    base.OnModelCreating(modelBuilder);
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<IdeaViewModel>()
        .HasOne(i => i.User)
        .WithMany()
        .HasForeignKey("UserId")
        .HasConstraintName("FK_IdeaViewModel_User");

    base.OnModelCreating(modelBuilder);
}

{
  "rules": {
    "chats": {
      "$chatId": {
        ".read": "request.auth != null && resource.data.users[request.auth.uid] == true",
        ".write": "request.auth != null && resource.data.users[request.auth.uid] == true"
      }
    }
  }
}

{
  "rules": {
    "chats": {
      "$chatId": {
        ".read": "request.auth != null && resource.data.users[request.auth.uid] == true",
        ".write": "request.auth != null && resource.data.users[request.auth.uid] == true"
      }
    }
  }
}