CC @0xb4lint

Hi, sorry if I misunderstand things. I'm looking at the "OptimizerChainFactory refactor with config processor" change from 1.7.3:
e74cdf1

The problem occurs when the config in OptimizerChainFactory::create($config) contains a 'quality' entry, which it can, according to the code in getOptimizers() below. Previously, such a "generic" quality would be applied to all optimizers that support it.

The call to the new self::configHasOptimizer($config) results in config being returned verbatim, including the 'quality' entry:
e74cdf1#diff-4f7d0501c10934549ecacfae146962d03a7dcacf1ffab4cadef7984a68409cdfR32

Then when this is instantiated, we get an attempt to call new quality(...) which fails with a ClassNotFoundErrror.
e74cdf1#diff-4f7d0501c10934549ecacfae146962d03a7dcacf1ffab4cadef7984a68409cdfR21

In short: Since 1.7.3 it is no longer possible to specify $config['quality'], doing so results in a crash.
Thanks for reading.