The `SecurityUserValueResolver` & `Psr7ServerRequestResolver` don't seem to be documented. The `SecurityUserValueResolver` was [documented for a while](https://github.com/symfony/symfony-docs/pull/7060), but the documentation was later [removed](https://github.com/symfony/symfony-docs/commit/df21fd8ecc6e7cbe2972c4e6395381e2bcddae27#diff-d1c69ceaea98cb0458d71feab0760245). Now, only the [blog post](https://symfony.com/blog/new-in-symfony-3-2-user-value-resolver-for-controllers) is left. As far as I can tell the `Psr7ServerRequestResolver` was never documented.