public class ChatMessage
    {
        [Key]
        public Guid Id { get; set; }
        public string SenderId { get; set; }
        public string ReceiverId { get; set; }
        public string Message { get; set; }
        public DateTime SendMessageDate { get; set; }
        public ChatConnection ConnectionId { get; set; }
    }


    public class ChatConnection
    {
        [Key]
        public Guid ConnectionId { get; set; }
        public string FirstItemId { get; set; }
        public string SecondItemId { get; set; }
    }