minor #10995 Update some articles related to user providers (javiereguiluz)

This PR was squashed before being merged into the 4.2 branch (closes #10995).

Discussion
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Update some articles related to user providers

This makes the security/user_provider.rst a reference article which explains everything about all user providers (except LDAP, which is complicated). This could simplify things because allows developers to read just one article to know all the basics about user providers.

If you are worried about the length of this single article ... don't worry ... the 500-line length is misleading because most of it is about `configuration-block`.

Commits
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0af54d5 Update some articles related to user providers

Author: javiereguiluz

_build/redirection_map

@@ -408,3 +408,4 @@
 /profiler/matchers /profiler
 /profiler/profiling_data /profiler
 /profiler/wdt_follow_ajax /profiler
+/security/entity_provider /security/user_provider

reference/configuration/security.rst

@@ -234,29 +234,10 @@ statically using the ``dn_string`` config option.
 User provider
 ~~~~~~~~~~~~~
 
-Users will still be fetched from the configured user provider. If you
-wish to fetch your users from a LDAP server, you will need to use the
-``ldap`` user provider, in addition to one of the three authentication
-providers (``form_login_ldap`` or ``http_basic_ldap`` or ``json-login-ldap``).
-
-.. configuration-block::
-
-    .. code-block:: yaml
-
-        # config/packages/security.yaml
-        security:
-            # ...
-
-            providers:
-                my_ldap_users:
-                    ldap:
-                        service: ldap
-                        base_dn: 'dc=symfony,dc=com'
-                        search_dn: '%ldap.search_dn%'
-                        search_password: '%ldap.search_password%'
-                        default_roles: ''
-                        uid_key: 'uid'
-                        filter: '(&({uid_key}={username})(objectclass=person)(ou=Users))'
+Users will still be fetched from the configured user provider. If you wish to
+fetch your users from a LDAP server, you will need to use the
+:doc:`LDAP User Provider </security/ldap>` and any of these authentication
+providers: ``form_login_ldap`` or ``http_basic_ldap`` or ``json_login_ldap``.
 
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