Add model translation for FormPage

Add model translations for the FormPage but not yet for the FormField model,
which doesn't work well, because the field name are translated along
with the label and different sets of data would be saved depending on
the user languages and different sets of data would be retrieved by the
vsc export depending on the admin language.

mpicms/base/translation.py

@@ -7,7 +7,10 @@
 from modeltranslation.translator import TranslationOptions
 from modeltranslation.decorators import register
 
-from .models import WikiPage, RootPage, HomePage, FeaturedImage, PhonelistPage
+from .models import (
+    WikiPage, RootPage, HomePage, FeaturedImage, PhonelistPage,
+    FormPage, FormField,
+)
 
 
 @register(FeaturedImage)
@@ -43,3 +46,10 @@ class PhonelistPageTR(TranslationOptions):
     fields = (
     )
 
+@register(FormPage)
+class FormPageTR(TranslationOptions):
+    fields = (
+        'sidebar',
+        'intro',
+        'thank_you_text',
+    )