TASK: Add changelog for 8.2.1 [skip ci]

See https://jenkins.neos.io/job/flow-release/396/

Neos.Flow/Documentation/TheDefinitiveGuide/PartV/ChangeLogs/821.rst

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+`8.2.1 (2023-02-23) <https://github.com/neos/flow-development-collection/releases/tag/8.2.1>`_
+==============================================================================================
+
+Overview of merged pull requests
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+`BUGFIX: isNewObject will correctly report object status <https://github.com/neos/flow-development-collection/pull/2700>`_
+--------------------------------------------------------------------------------------------------------------------------
+
+With this change ``PersistenceManager::isNewObject`` will correctly report object status in all circumstances.
+
+* Fixes: `#2699 <https://github.com/neos/flow-development-collection/issues/2699>`_
+
+* Packages: ``Flow``
+
+`BUGFIX: Reset cache backend iterator state on update <https://github.com/neos/flow-development-collection/pull/2884>`_
+-----------------------------------------------------------------------------------------------------------------------
+
+Some cache backends hold an internal state when used as an iterator.
+This state needs to be reset whenever the source data is updated.
+
+
+* Packages: ``Flow`` ``Cache``
+
+`BUGFIX: Support PHP8 union and intersection types as method return value in reflection service <https://github.com/neos/flow-development-collection/pull/2944>`_
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------
+
+The change allows to use union types and intersection types in classes which are proxied by the flow framework. 
+Offcourse the php version Flow is running on has to support the used features aswell.
+
+In addition: 
+- ``true``, ``false`` and ``null`` are added to the list of simple types which are not prefixed by the reflection service
+- ``parent``, ``static``, ``never`` and ``resource`` are added to the list of additional types that need no prefix during reflection aswell
+
+* Resolves: `#2941 <https://github.com/neos/flow-development-collection/issues/2941>`_ 
+
+**Upgrade instructions**
+
+
+* Packages: ``Flow``
+
+`BUGFIX: Fix truncation of cache file when lock not acquired <https://github.com/neos/flow-development-collection/pull/2933>`_
+------------------------------------------------------------------------------------------------------------------------------
+
+Previously, SimpleFileBackend would truncate the contents of the cache file if it couldn't acquire the lock.
+
+To fix this, the ``c`` flag is used for ``fopen``, so the file is not truncated if it already exists. This necessitates that we manually truncate the file if the lock is acquired.
+
+I've added a test that fails without these changes, and passes with them.
+
+
+* Packages: ``Flow`` ``Cache``
+
+`BUGFIX: Support empty data in SimpleFileBackend <https://github.com/neos/flow-development-collection/pull/2934>`_
+------------------------------------------------------------------------------------------------------------------
+
+In newer versions of PHP, calling ``fread`` with non-positive length raises an error:
+``fread(): Argument ``#2 <https://github.com/neos/flow-development-collection/issues/2>``_($length) must be greater than 0``
+
+Since SimpleFileBackend supports saving an empty file, it should also support reading one.
+
+I've added a test that fails without these changes.
+
+* Fixes: `#2929 <https://github.com/neos/flow-development-collection/issues/2929>`_ 
+
+
+* Packages: ``Flow`` ``Cache``
+
+`TASK: Adding labels to PRs <https://github.com/neos/flow-development-collection/pull/2959>`_
+---------------------------------------------------------------------------------------------
+
+With this task, we add automatically labels to the PRs. That makes the maintaining easier, as we did that manually all the time.
+
+*What I did*
+We always add the target branch as label, so we see directly which version the PR targets. And if the Commit message is following our rules, we also add the bugfix, task or feature label.
+
+*How I did it*
+I use the runner from https://github.com/actions-ecosystem They use node 12 which leads to a warning as actions are running node 16 but an issue is created and it runs anyways.
+
+*How to verify it*
+Checkout how it works in the neos-ui.
+https://github.com/neos/neos-ui/pull/3387
+
+- [ ] Reviewer - Breaking Changes are marked with ``!!!`` and have upgrade-instructions
+
+* Packages: ``Flow`` ``.github``
+
+`TASK: Handle ReflectionUnionType & ReflectionIntersectionType <https://github.com/neos/flow-development-collection/pull/2808>`_
+--------------------------------------------------------------------------------------------------------------------------------
+
+This adds explicit handling of ``ReflectionUnionType`` & ``ReflectionIntersectionType`` instead of falling back to the deprecated ``__toString()`` method on ``ReflectionType``.
+
+Since we do no longer suppport PHP < 7.1 only the two mentioned types as well as ``ReflectionNamedType`` are supported, a "pure" ``ReflectionType`` can no longer be present at this point.
+
+* Packages: ``Flow``
+
+`TASK: Add logging to TaggableMultiBackend.buildSubBackend <https://github.com/neos/flow-development-collection/pull/2896>`_
+----------------------------------------------------------------------------------------------------------------------------
+
+**Review instructions**
+
+With an incorrect backend configured, a message should be logged.
+
+
+* Packages: ``Flow`` ``Cache``
+
+`TASK: Add PHP 8.1 & 8.2 to CI build <https://github.com/neos/flow-development-collection/pull/2942>`_
+------------------------------------------------------------------------------------------------------
+
+
+
+* Packages: ``Flow`` ``Cache``
+
+`Detailed log <https://github.com/neos/flow-development-collection/compare/8.2.0...8.2.1>`_
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~