Copy function for view only pages - #1202

Thanks for offering this pull request @mark-james. To properly cover the issue this is going to need some deeper changes.

We can't simply check the page-create-* or page-view role permissions, Since these changes have the possibility to show the actions for those that cannot actually use them. These permissions also don't take into account the entity-level permissions.

BookStack keeps a record of role-to-entity permissions in the joint_permissions table. This will need to be looked-up for each of the current user's roles.

Thanks for the feedback @ssddanbrown , I'll use the joint_permissions table as you suggest.

I'm a little fuzzy on why. Is it because just using the role permissions doesn't account for pages that have been overridden? Is this what you mean by entity level?

I'm assuming taking this approach also handles at least part of the issue I raised initially - "when a user attempts to copy a page but does not have an existing destination available to copy it too"? Eg. They can create pages but don't currently have a available book to do so.

Finally how do you want me to handle the scenario when a user doesn't select a destination to copy the page too. We could either -

1. Disable the copy button until something is selected.
2. Default to the first destination on the list
3. Show a popup error message indicating the user doesn't have permission to copy the page to the existing book so they need to select a destination.
4. Or is there another alternative?

Hi @ssddanbrown , I've updated to use the joint_permissions table. It's all done in one query so it should be performant. I've confirmed that it works with overridden permissions.

Have I understood the requirements correctly?

Thanks for this @mark-james, Sorry for the delay in my response.

Your latest changes did exactly what I desired in my last comment so all way good-to-go.
I did abstract the implementation since we'll be doing similar checks for other permissions and I also added a test. My changes can be seen in 5c9b528.

The will be in the next patch release.