Ajout groupes K-Fêt utilisateurs en lecture

- Pour voir les groupes, il faut la permission `kfet.manage_perms`
- Pour modifier les groupes auxquels fait parti un compte, il la faut
  également

kfet/forms.py

@@ -1,6 +1,6 @@
 from django import forms
 from django.core.exceptions import ValidationError
-from django.contrib.auth.models import User
+from django.contrib.auth.models import User, Group
 from django.forms import modelformset_factory
 from kfet.models import (Account, Checkout, Article, OperationGroup, Operation,
     CheckoutStatement)
@@ -78,9 +78,20 @@ class UserForm(forms.ModelForm):
         }
 
 class UserRestrictForm(UserForm):
+    class Meta(UserForm.Meta):
+        fields = ['first_name', 'last_name']
+
+class UserRestrictTeamForm(UserForm):
     class Meta(UserForm.Meta):
         fields = ['first_name', 'last_name', 'email']
 
+class UserGroupForm(forms.ModelForm):
+    groups = forms.ModelMultipleChoiceField(
+            Group.objects.filter(name__icontains='K-Fêt'))
+    class Meta:
+        model  = User
+        fields = ['groups']
+
 # -----
 # Checkout forms
 # -----