Fewer requests on create/update spectaclerevente in bda admin.

- O(#participant) -> O(1) requests

bda/admin.py

@@ -230,6 +230,24 @@ class SalleAdmin(admin.ModelAdmin):
     search_fields = ('name', 'address')
 
 
+class SpectacleReventeAdminForm(forms.ModelForm):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.fields['answered_mail'].queryset = (
+            Participant.objects
+            .select_related('user', 'tirage')
+        )
+        self.fields['seller'].queryset = (
+            Participant.objects
+            .select_related('user', 'tirage')
+        )
+        self.fields['soldTo'].queryset = (
+            Participant.objects
+            .select_related('user', 'tirage')
+        )
+
+
 class SpectacleReventeAdmin(admin.ModelAdmin):
     """
     Administration des reventes de spectacles
@@ -252,6 +270,7 @@ class SpectacleReventeAdmin(admin.ModelAdmin):
 
     actions = ['transfer', 'reinit']
     actions_on_bottom = True
+    form = SpectacleReventeAdminForm
 
     def transfer(self, request, queryset):
         """