The override_required decorator was implemented instead of using the abc
module due to its instability, however, unlike @abstractmethod from abc
it does allow class instantiation even though the method was not
overriden.

as the json structure stored is not specific to any database management
system.

to prevent clashing of underscores in client names and underscores used by LIKE.

In MYSQL 8.0 one cannot create users using GRANT.
https://dev.mysql.com/doc/refman/8.0/en/mysql-nutshell.html#mysql-nutshell-removals
(MariaDB worked fine)

This did not work for python 3.9 and 3.10 (each for a different reason)
The context management of the cursor, seems to have been an undocumented feature
for at least six years.

* Needed to correctly support UTF-8 ReadableSTR decoding on Py3

* Introduced in 5f2e50a0
* Caused the POST payload to be always ignored, breaking the function completely.
* Great job finding and debugging this, Honza Žerdík.

Fixes wrong references in embedded (dict in dict) class variables
outside the class variable definition context, for redefined
inherited class variables.

Aimed mainly at web method invocation (similar to warden_curl_test.sh
from warden_client) and some command line interface commands.

Shuffle directories and filenames to get rid of historic cruft and to better reflect contrib/production status