Feature/add single item to collection

[damilare]

• This pull requests adds a content_object (page as an illustration)
• Integration with versioning is stubbed out at the moment.

[mmoravcik]

When creating a new collection, the author field should not be visible and should be prepopulated with the current user who is creating the collection. Also fields like is_locked and status in the future should not be a part of this dialog

[mmoravcik]

When assigning an item to a collection, there is an option to create a new collection using the + button. Once I create it and hit submit, I'd expect my item to be part of this newly created collection - instead the dialog disappears and I don't really know what happened

[mmoravcik]

I am also missing some confirmation message e.g. messages.success('Your item has been added to the Collection XXX')

[damilare]

@mmoravcik I have covered those cases with Kuldeep and he is happy with that behavior for now, and also for the message feedback, it was WIP when you tried it, pls pull and check again.

[czpython]

Looks good 💯 💯 💯

[chaosk]

You're on fire! 🔥🚨🔥

[0mk1]

✌️✌️✌️

[monikasulik]

Excellent, this is so good that we won't have to feed you to :crocodile: or :crab:! Have a :croissant: and :cake: you so deserve it!