Since MDL-85533, the activity chooser now classifies the activities according to their purpose. However, each activity can only have one purpose.

The project's protoype contemplates the possibility to add extra pruposes to a plugin. When this happens, the category shows an extra list called "Related activities" that list other plugins.

This issue will be implemented over the MDL.-85533 code and will:

• Add the extra purposes feature to the activity plugins. Each plugin should be able to return an array of extra purposes.
• Modify the current core_course_get_course_content_items webservice by adding the extra purposes as a new attribute to each activity item.
• Render the "realted activities" in the activity chooser tab.
• Modify the keyboard navigation implemented in course/amd/src/local/activitychooser/dialogue.js to allow access to the related activities list. Currently, it can only navigate to sibling elements.
• Add behat and phpunit tests.