add image and preface fields to proceedings form

scipost_django/proceedings/forms.py

@@ -22,6 +22,12 @@ class ProceedingsForm(forms.ModelForm):
             "submissions_deadline",
             "submissions_close",
             "template_latex_tgz",
+            "logo",
+            "cover_image",
+            "picture",
+            "picture_credit",
+            "preface_title",
+            "preface_text",
         )
         widgets = {
             "submissions_open": forms.DateInput(attrs={"type": "date"}),
@@ -30,3 +36,9 @@ class ProceedingsForm(forms.ModelForm):
             "event_start_date": forms.DateInput(attrs={"type": "date"}),
             "event_end_date": forms.DateInput(attrs={"type": "date"}),
         }
+        help_texts = {
+            "logo": "Upload a logo for the proceedings.",
+            "cover_image": "Upload a cover image, e.g. the first cover page of the issue, for the proceedings.",
+            "picture": "Upload a centered picture for the proceedings.",
+            "preface_text": "HTML content of the preface.",
+        }