This issue is part of the course hierarch project.

Issue goals

After MDL-82259, when a section is hidden all its subsection are also hidden.

However, if the user creates a subsection inside a hidden subsection the behaviour is quite erratic. The subsection is created as visible but it won't change even if the parent section is back to visible and then hidden again.

Steps to reproduce:

1. Create a course with one visible section
2. Create a subsection 1 inside the section. The new subsection 1 is created visible as expected.
3. Now hide the parent section. Subsection 1 is hidden as expected.
4. Now create a new subsection 2 inside the hidden section.
   1. Expected: the new subsection 2 is created as hidden
   2. What happens: subsection 2 is created visible ( no hidden badge is displayed)
5. Then unhide (show) the parent section. Both subsections are again visible as expected (subsection 1 turns visible and subsection 2 does not change).
6. Hide again the parent section
   1. Expected: both subsections hide
   2. What happens: subsection 1 hides but subsection 2 remains visible.