forms: use djago-select2 field for selecting the collectivity

fixes #7289

setup.py

@@ -111,6 +111,7 @@ setup(name='authentic2-pratic',
         },
         install_requires=[
             'authentic2',
+            'django-select2>4.3.0',
         ],
         entry_points={
             'authentic2.plugin': [

src/authentic2_pratic/fields.py

@@ -0,0 +1,7 @@
+from django_select2 import AutoModelSelect2Field
+
+from . import models
+
+class CollectivityField(AutoModelSelect2Field):
+    queryset = models.Collectivity.objects
+    search_fields = ['name__icontains']

src/authentic2_pratic/forms.py

@@ -7,7 +7,7 @@ from django.utils.translation import ugettext_lazy as _, ugettext
 
 from django.contrib.auth import authenticate
 
-from . import models
+from . import models, fields
 
 class BaseForm(forms.ModelForm):
     required_css_class = 'required'
@@ -81,8 +81,9 @@ class UserForm(CertificateMixin, BaseForm):
 class AuthenticationForm(forms.Form):
     how = None
 
-    collectivity = forms.ModelChoiceField(queryset=models.Collectivity.objects,
-            label=_('Collectivity'))
+    collectivity = fields.CollectivityField(
+        queryset=models.Collectivity.objects,
+        label=_('Collectivity'))
     username = forms.CharField(label=_('Username'))
     password = forms.CharField(label=_('Password'), widget=forms.PasswordInput)