Register MultipleChoiceField as list type (#1033)

In general I welcome reviews even from non-maintainers to build confidence. I haven't seen any objections and this has sat with approval for a week so I am going to go ahead and merge.

Author: ulgens

graphene_django/forms/converter.py

@@ -63,6 +63,11 @@ def convert_form_field_to_list(field):
     return List(ID, required=field.required)
 
 
+@convert_form_field.register(forms.MultipleChoiceField)
+def convert_form_field_to_string_list(field):
+    return List(String, required=field.required)
+
+
 @convert_form_field.register(forms.DateField)
 def convert_form_field_to_date(field):
     return Date(description=field.help_text, required=field.required)

graphene_django/forms/tests/test_converter.py

@@ -101,7 +101,14 @@ def test_should_decimal_convert_float():
     assert_conversion(forms.DecimalField, Float)
 
 
-def test_should_multiple_choice_convert_connectionorlist():
+def test_should_multiple_choice_convert_list():
+    field = forms.MultipleChoiceField()
+    graphene_type = convert_form_field(field)
+    assert isinstance(graphene_type, List)
+    assert graphene_type.of_type == String
+
+
+def test_should_model_multiple_choice_convert_connectionorlist():
     field = forms.ModelMultipleChoiceField(queryset=None)
     graphene_type = convert_form_field(field)
     assert isinstance(graphene_type, List)