[Monolog] Mention the SwitchUserTokenProcessor

Author: javiereguiluz

logging/processors.rst

@@ -171,6 +171,14 @@ Symfony's MonologBridge provides processors that can be registered inside your a
     Adds information from the current user's token to the record namely
     username, roles and whether the user is authenticated.
 
+:class:`Symfony\\Bridge\\Monolog\\Processor\\SwitchUserTokenProcessor`
+    Adds information about the user who is impersonating the logged in user,
+    namely username, roles and whether the user is authenticated.
+
+    .. versionadded:: 5.2
+
+        The ``SwitchUserTokenProcessor`` was introduced in Symfony 5.2.
+
 :class:`Symfony\\Bridge\\Monolog\\Processor\\WebProcessor`
     Overrides data from the request using the data inside Symfony's request
     object.