First interface to start draws

Signed-off-by: Emmy D'Anello <emmy.danello@animath.fr>

participation/models.py

@@ -278,6 +278,13 @@ class Tournament(models.Model):
             return Synthesis.objects.filter(final_solution=True)
         return Synthesis.objects.filter(participation__tournament=self)
 
+    @property
+    def best_format(self):
+        n = len(self.participations.filter(valid=True).all())
+        fmt = [n] if n <= 5 else [3] * (n // 3 - 1) + [3 + n % 3]
+        return '+'.join(map(str, fmt))
+
+
     def get_absolute_url(self):
         return reverse_lazy("participation:tournament_detail", args=(self.pk,))