Don't access to team participation if the team is not validated

apps/participation/models.py

@@ -80,6 +80,13 @@ class Participation(models.Model):
         verbose_name=_("problem number"),
     )
 
+    valid = models.BooleanField(
+        null=True,
+        default=None,
+        verbose_name=_("valid"),
+        help_text=_("The video got the validation of the administrators."),
+    )
+
     solution = models.OneToOneField(
         "participation.Video",
         on_delete=models.SET_NULL,