minor #7206 Added docs for the cache:pool:clear command (javiereguiluz, HeahDude)

This PR was merged into the 3.2 branch.

Discussion
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Added docs for the cache:pool:clear command

This fixes #7173.

Commits
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3c31e09 applying comment from @wouterj
2c220c4 Added docs for the cache:pool:clear command

Author: xabbuh

components/cache/cache_pools.rst

@@ -343,4 +343,19 @@ when all items are successfully deleted)::
     // ...
     $cacheIsEmpty = $cache->clear();
 
+.. tip::
+
+    If the Cache component is used inside a Symfony application, you can remove
+    all the items of a given cache pool with the following command:
+
+    .. code-block:: terminal
+
+        $ php bin/console cache:pool:clear <cache-pool-name>
+        
+        # clears the "cache.app" pool
+        $ php bin/console cache:pool:clear cache.app
+
+        # clears the "cache.validation" and "cache.app" pool
+        $ php bin/console cache:pool:clear cache.validation cache.app
+
 .. _`Doctrine Cache`: https://github.com/doctrine/cache