minor #15502 Fix doc of cache prefix and namespace (Tobion)

This PR was merged into the 4.4 branch.

Discussion
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Fix doc of cache prefix and namespace

Commits
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1a3e544 Fix doc of cache prefix and namespace

Author: javiereguiluz

cache.rst

@@ -305,8 +305,8 @@ You can also create more customized pools:
 Each pool manages a set of independent cache keys: keys from different pools
 *never* collide, even if they share the same backend. This is achieved by prefixing
 keys with a namespace that's generated by hashing the name of the pool, the name
-of the compiled container class and a :ref:`configurable seed <reference-cache-prefix-seed>`
-that defaults to the project directory.
+of the cache adapter class and a :ref:`configurable seed <reference-cache-prefix-seed>`
+that defaults to the project directory and compiled container class.
 
 Each custom pool becomes a service whose service ID is the name of the pool
 (e.g. ``custom_thing.cache``). An autowiring alias is also created for each pool

reference/configuration/framework.rst

@@ -2485,7 +2485,7 @@ email_validation_mode
 
 **type**: ``string`` **default**: ``loose``
 
-Sets the default value for 
+Sets the default value for
 :doc:`/reference/constraints/Email` validator. The possible values are:
 
 * ``loose``, it uses a simple regular expression to validate the address (it
@@ -2938,9 +2938,9 @@ The cache clearer used to clear your PSR-6 cache.
 prefix_seed
 ...........
 
-**type**: ``string`` **default**: ``null``
+**type**: ``string`` **default**: ``_%kernel.project_dir%.%kernel.container_class%``
 
-If defined, this value is used as part of the "namespace" generated for the
+This value is used as part of the "namespace" generated for the
 cache item keys. A common practice is to use the unique name of the application
 (e.g. ``symfony.com``) because that prevents naming collisions when deploying
 multiple applications into the same path (on different servers) that share the