minor #11355 Fix resolve example (jderusse)

This PR was merged into the 3.4 branch.

Discussion
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Fix resolve example

The `resolve` processor can only resolve `parameters` whereas the documentation give the feeling that we could resolve env variables too. Wich is not the case (see symfony/symfony#31000).

This PR change the example in order to be unambiguous.

Commits
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3e60b9d Fix resolve example

Author: OskarStark

configuration/external_parameters.rst

@@ -377,7 +377,8 @@ Symfony provides the following env var processors:
             # config/packages/sentry.yaml
             parameters:
                 env(HOST): '10.0.0.1'
-                env(SENTRY_DSN): 'http://%env(HOST)%/project'
+                sentry_host: '%env(HOST)%'
+                env(SENTRY_DSN): 'http://%sentry_host%/project'
             sentry:
                 dsn: '%env(resolve:SENTRY_DSN)%'
 
@@ -392,7 +393,8 @@ Symfony provides the following env var processors:
 
                 <parameters>
                     <parameter key="env(HOST)">10.0.0.1</parameter>
-                    <parameter key="env(SENTRY_DSN)">http://%env(HOST)%/project</parameter>
+                    <parameter key="sentry_host">%env(HOST)%</parameter>
+                    <parameter key="env(SENTRY_DSN)">http://%sentry_host%/project</parameter>
                 </parameters>
 
                 <sentry:config dsn="%env(resolve:SENTRY_DSN)%"/>
@@ -402,7 +404,8 @@ Symfony provides the following env var processors:
 
             // config/packages/sentry.php
             $container->setParameter('env(HOST)', '10.0.0.1');
-            $container->setParameter('env(SENTRY_DSN)', 'http://%env(HOST)%/project');
+            $container->setParameter('sentry_host', '%env(HOST)%');
+            $container->setParameter('env(SENTRY_DSN)', 'http://%sentry_host%/project');
             $container->loadFromExtension('sentry', [
                 'dsn' => '%env(resolve:SENTRY_DSN)%',
             ]);