auth_saml: move model form parameters to class (#53442)

src/authentic2_auth_saml/forms.py

@@ -17,6 +17,7 @@
 from django import forms
 
 from authentic2.a2_rbac.models import Role
+from authentic2.forms.widgets import SelectAttributeWidget
 from authentic2.manager.utils import label_from_role
 
 from .models import SAMLAuthenticator
@@ -65,3 +66,10 @@ class RoleChoiceField(forms.ModelChoiceField):
 
     def label_from_instance(self, obj):
         return label_from_role(obj)
+
+
+class SAMLRelatedObjectForm(forms.ModelForm):
+    class Meta:
+        exclude = ('authenticator',)
+        field_classes = {'role': RoleChoiceField}
+        widgets = {'user_field': SelectAttributeWidget}

src/authentic2_auth_saml/views.py

@@ -7,11 +7,10 @@ from django.urls import reverse
 from django.views.generic import CreateView, DeleteView, UpdateView
 from mellon.utils import get_idp
 
-from authentic2.forms.widgets import SelectAttributeWidget
 from authentic2.manager.views import MediaMixin, TitleMixin
 from authentic2.utils.misc import redirect_to_login
 
-from .forms import RoleChoiceField
+from .forms import SAMLRelatedObjectForm
 from .models import AddRoleAction, SAMLAttributeLookup, SAMLAuthenticator, SetAttributeAction
 
 
@@ -60,12 +59,7 @@ class SAMLAuthenticatorMixin(MediaMixin, TitleMixin):
         return super().dispatch(request, *args, **kwargs)
 
     def get_form_class(self):
-        return modelform_factory(
-            self.model,
-            exclude=('authenticator',),
-            field_classes={'role': RoleChoiceField},
-            widgets={'user_field': SelectAttributeWidget},
-        )
+        return modelform_factory(self.model, SAMLRelatedObjectForm)
 
     def get_form_kwargs(self):
         kwargs = super().get_form_kwargs()