While this change is not 100% required now, it's good habit
and we are checking for it since Moodle 4.4.
All the changes in this commit have been applied automatically
using the moodle.PHPUnit.TestReturnType sniff and are, exclusively
adding the ": void" return types when missing.
This chagne adds support for a new feature known as Context Locking.
This allows a context to be locked, thereby removing all write
capabilities for all users (including admin) for that context, and all
child contexts.
Andrew Nicols