Backlinks: should not have required fields

In models.py some models currently have required fields (like Poll.title). This will cause errors accessing backlinked objects, which currently do not support required fields

ping @balessan

changed the description

added BUG label

Error on a production server caused by this: http://51.15.253.90:9000/organizations/hubl/issues/25/?query=is%3Aunresolved

It's trying to save a backlinked object which doesn't define a required field (because backlinks are just a urlid)

Ping @Senza ?

heyhey, this is related to SIB versions i believe. Since the versions changed, if memory serves a makemigrations should remove the backlink field

Hi! The issue is that fields like title are set to NOT NULL, please see this issue for context: djangoldp-packages/djangoldp#224