Merge branch 'update' into 'master'

.gitlab-ci.yml

composer.json

phpstan.neon

src/ExternalSerializer/SerializerList.php

src/Mapper/DeferredAssertionsMapper.php

src/PayloadMetadata.php

src/PayloadProcessor.php

...RemovedClassesDeserializer/RemovedClassesDeserializer.php

src/State.php

src/StateBuilder.php

src/Tools.php

src/exceptions.php

tests/Stateful/Mapper/DeferredAssertionsMapperTest.phpt