Authenticate user everywhere but index and show actions.
Merge branch 'authenticate-user-on-most-actions'
Add 'cancan' dependency (autorisation)
Run `r g cancan:ability`
Run `magic_encoding`
Let authors edit/update/destroy only their own Problems/Analyses/Solutions/Opinions
Rescue from AccessDenied message. Let users read and create everything.
Merge branch 'introduce-authorisation'