A viewer clicking a draft/scheduled post landed on the editor route
(authorizes update) and got a 403. The post list/calendar routed every
editable post to the edit page, and PostController@show redirected
draft/scheduled posts to the editor for everyone.
- show only redirects to the editor when the user can update the post;
viewers get the read-only Show page
- posts index + calendar route to show (not edit) when the user cannot
create posts
- cover viewer-sees-show, member-redirected-to-editor, and
viewer-403-on-direct-edit in WorkspaceRolePermissionsTest
8b52ea2082