As a teacher
I want to be able to hide and show an activity
so the learners can't see the activities are not ready and see the content once is ready

Toggles visibility of an activity:

• Between ‘Show on course page’ and ‘Hide from students’ when the activity is into a visible section.
• Between ‘Make available but not shown on course page’ and ‘Hide from students’ when the activity is into a visible section.

(forget about the rest of options for now)

Prototype: https://www.figma.com/proto/OfCvqK069Oz6Fvqq2xcZWI/Create-a-course?node-id=3285%3A38308&scaling=scale-down

Acceptance criteria:

1. User needs permissions to hide and show activities.
2. Activity's visibility will be changed in the course index and course main content.

Technical tasks:

• Add cm_hide and cm_show state actions