Issue 54: Add GDPR support

[golenkovm]

This is to fix the issue #54

Core unit tests are passing:

root@cf7f7c4e89bd:/var/www/site# vendor/bin/phpunit --testsuite='core_privacy_testsuite'
Moodle 3.9.11 (Build: 20211108), 2f59059095d9a1779195e2d3df6c19b399413ed3
Php: 7.4.25, pgsql: 9.6.16, OS: Linux 5.4.0-89-generic x86_64
PHPUnit 7.5.20 by Sebastian Bergmann and contributors.

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...                                                           1528 / 1528 (100%)

Time: 51.02 seconds, Memory: 161.00 MB

OK (1528 tests, 10901 assertions)