Currently it is not necessary to include the link_url field.
When we display these cards without link_url, they create an empty link that
redirects to the same page. I understand that this is not a desired behavior, so I
think it is better to add a validation in this case and force administrators to add a
link_url when creating a card.
These cards will be displayed in the SDG homepage.
Note there seems to be a strange behavior in cancancan. If we define
these rules:
can :manage, Widget::Card, page_type: "SDG::Phase"
can :manage, Widget::Card
The expected behavior is the first rule will always be ignored because
the second one overwrites it. However, when creating a new card with
`load_and_authorize_resource` will automatically add `page_type:
"SDG::Phase"`.
Similarly, if we do something like:
can :manage, Widget::Card, id: 3
can :manage, Widget::Card
Then the new card will have `3` as an ID.
Maybe upgrading cancancan solves the issue; we haven't tried it. For now
we're defining a different rule when creating widget cards.
