Improve conflicts admin (while waiting for new COI system)

conflicts/admin.py

@@ -8,7 +8,13 @@ from .models import ConflictOfInterest
 
 
 class ConflictAdmin(admin.ModelAdmin):
-    search_fields = ('header', 'profile__last_name', 'related_profile__last_name')
+    search_fields = (
+        'header',
+        'profile__last_name',
+        'related_profile__last_name',
+        'related_submissions__title',
+        'related_submissions__preprint__identifier_w_vn_nr'
+    )
     list_filter = ('status', 'type')
     list_display = ('header', 'profile', 'related_profile', 'status', 'type')