Changes since 2.1.0: https://github.com/wikimedia/object-factory/compare/v2.1.0...v3.0.0
Notable changes:
Support for optional services
Removed deprecated `constructClassInstance` method
Allow null values for 'services' spec field
Drop PHP 7.0/7.1 and HHVM support
Checklist:
[x] Update HISTORY.md {icon check-square color=green} [patch](https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/libs/ObjectFactory/+/0d2c4efc08e80485e5f7b1665fe473375e242017)
[x] Tag new version {icon check-square color=green} [Tagged by @Jdforrester-WMF](https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/libs/ObjectFactory/+/refs/tags/v3.0.0)
[x] Update Parsoid to accept either old or new version of ObjectFactory {icon check-square color=green} [patch](https://gerrit.wikimedia.org/g/mediawiki/services/parsoid/+/b0a43f6683d5e7de9e7cbf44afe1a2919b9639d6)
[] Update vendor with new version of Parsoid
[] Update vendor with new version of ObjectFactory
[] Update core with new version of ObjectFactory
[] Update `HookHandlers`' `additionalProperties` schema in `extension.schema.v1.json` and `extension.schema.v2.json` (no such clear schema is included for the other fields that accept ObjectFactory specs)
[] Update `HookContainer::getHandlers` check for hooks called with `noServices` also object to `optional_services` being set
[] Update `Router::createHandler` to allow the `optional_services` key
[] Update documentation of `onLoadExtensionSchemaUpdates` hook to object to `optional_services`