Category taxonomy's detail page doesn't take hierarchy into account

Problem/Motivation

The detail page of the Category taxonomy lists related events, locations, artists, and others. But it doesn't take into account that there is a term hierarchy. So entities linked with a subcategory aren't shown.

Steps to reproduce

1. Install OpenCulturas with default content
2. Create a few events(, locations, artists, …) and assign them to the category Rock and pop music, which is a subcategory of Music.
3. Open the detail page for the Music category (/en/categories/music)

Expected result

All entities created in step 2 will be shown.

Actual result

No entities are shown, because they are releated to a subcategory.

Proposed resolution

Use a hierarchy context filter with a depth of 1.

Remaining tasks

• Write patch
• Review
• Commit