Make room for domain code.
Create CommandParamConverter.
Use CommandParamConverter to pass command objects to controller.
Convert BadCommandRequestExceptions to JSON responses.
Rename Command#__uuid to #UUID so as to not trip up PHPCS (...)

... with every command you create.
Adjust QA tools configuration.
Install Mockery.
Make CommandParamConverter command namespace configurable.
Test CommandParamConverter.
Exclude tests from Scrutinizer.
Move classes into correct directories as per new namespace structure.