minor #8235 Document new Monolog HTTP code exclusion feature (simshaun, javiereguiluz)

This PR was merged into the 4.1 branch.

Discussion
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Document new Monolog HTTP code exclusion feature

I'm submitting PRs on symfony/symfony and symfony/monolog-bundle that introduces an easy way of excluding specific HTTP codes from Monolog.

This PR documents that new feature, pending its acceptance.

Pending PRs:
symfony/symfony#23707
symfony/monolog-bundle#221

Commits
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30cc7d4 Added the versionadded directive
c8c19f2 Update to Symfony 4 paths
e19bca2 Fix indentation
17cb416 Update configuration format to support URL blacklist
c9f6ee5 Fix title underline length
a3b6a01 Document new Monolog HTTP code exclusion feature

Author: javiereguiluz

logging/monolog_exclude_http_codes.rst

@@ -0,0 +1,65 @@
+.. index::
+   single: Logging
+   single: Logging; Exclude HTTP Codes
+   single: Monolog; Exclude HTTP Codes
+
+How to Configure Monolog to Exclude Specific HTTP Codes from the Log
+====================================================================
+
+..versionadded:: 4.1
+    The ability to exclude log messages based on their status codes was
+    introduced in Symfony 4.1 and MonologBundle 3.3.
+
+Sometimes your logs become flooded with unwanted HTTP errors, for example,
+403s and 404s. When using a ``fingers_crossed`` handler, you can exclude
+logging these HTTP codes based on the MonologBundle configuration:
+
+.. configuration-block::
+
+    .. code-block:: yaml
+
+        # config/packages/prod/monolog.yaml
+        monolog:
+            handlers:
+                main:
+                    # ...
+                    type: fingers_crossed
+                    handler: ...
+                    excluded_http_codes: [403, 404, { 400: ['^/foo', '^/bar'] }]
+
+    .. code-block:: xml
+
+        <!-- config/packages/prod/monolog.xml -->
+        <container xmlns="http://symfony.com/schema/dic/services"
+            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+            xmlns:monolog="http://symfony.com/schema/dic/monolog"
+            xsi:schemaLocation="http://symfony.com/schema/dic/services
+                http://symfony.com/schema/dic/services/services-1.0.xsd
+                http://symfony.com/schema/dic/monolog
+                http://symfony.com/schema/dic/monolog/monolog-1.0.xsd">
+
+            <monolog:config>
+                <monolog:handler type="fingers_crossed" name="main" handler="...">
+                    <!-- ... -->
+                    <monolog:excluded-http-code code="403">
+                        <monolog:url>^/foo</monolog:url>
+                        <monolog:url>^/bar</monolog:url>
+                    </monolog:excluded-http-code>
+                    <monolog:excluded-http-code code="404" />
+                </monolog:handler>
+            </monolog:config>
+        </container>
+
+    .. code-block:: php
+
+        // config/packages/prod/monolog.php
+        $container->loadFromExtension('monolog', array(
+            'handlers' => array(
+                'main' => array(
+                    // ...
+                    'type'                => 'fingers_crossed',
+                    'handler'             => ...,
+                    'excluded_http_codes' => array(403, 404),
+                ),
+            ),
+        ));