Entity framework exception while creating a many to many relation

public class Transporteur : IdentityUser
    {
        public string Nom { get; set; } = string.Empty;
        public string Prenom { get; set; } = string.Empty;

        public Vehicule? Vehicule { get; set; }
        public string? VehiculeId { get; set; } = string.Empty;
        public bool ExterneDuService { get; set; } = false;
        public List<Voyage> Voyages { get; } = [];
        public ICollection<TransporteurVoyage> TransporteurVoyages { get; } = [];
    }
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public class Voyage
    {
        [Key]
        public string IdVoyage { get; set; } = string.Empty;
        public DateTime DateSortieBon { get; set; }
        public DateTime DateDepartVoyage { get; set; }

        public string Etat { get; set; } = string.Empty;
        //Demandeur
        public Demandeur Demandeur { get; set; } = null!;
        public string DemandeurId { get; set; } = string.Empty;
        //public ICollection<Utilisateur> Utilisateurs { get; set; } = new List<Utilisateur>();
        public Magasinier Magasinier { get; set; } = null!;
        public string IdMagasinier { get; set; } = string.Empty;
        public TypeVoyage TypeVoyage { get; set; } = null!;
        public int TypeVoyageId { get; set; }
        public List<Transporteur> Transporteurs { get; } = [];
        public ICollection<TransporteurVoyage> TransporteurVoyages { get; } = [];


    }
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public class TransporteurVoyage
    {
        public string TransporteurId { get; set; } = string.Empty;
        public string VoyageId { get; set; } = string.Empty;
        public bool Panne { get; set; } = false;
        public Voyage Voyage { get; set; } 
        public Transporteur Transporteur { get; set; }

    }