added tests for db and user

Backend/endpoints/user-session.go

@@ -53,7 +53,7 @@ func loginUser(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	user, err := (*models.User).GetByPersonalNummer(nil, personal_nummer)
+	user, err := models.GetUserByPersonalNr(personal_nummer)
 	if err != nil {
 		log.Println("No user found under this personal number!")
 		http.Error(w, "No user found!", http.StatusNotFound)