bug #19204 [Security] Allow LDAP loadUser override (tucksaun)

This PR was merged into the 3.1 branch.

Discussion
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[Security] Allow LDAP loadUser override

| Q             | A
| ------------- | ---
| Branch?       | 3.1
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Back to 3.0, one could extend `Symfony\Component\Security\Core\User\LdapUserProvider` and override how User objects are created.
Among several improvements, #17560 changed `loadUser` signature but also visibility to `private` which disallow any overriding.
Even if the signature BC break is legitimate, we should still be able to override this method IMHO, which is not possible with a private visibility.
This PRs introduces a `protected` visibility to allow again overriding.

Commits
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ae99aa8 [Security] Allow LDAP loadUser override

src/Symfony/Component/Security/Core/User/LdapUserProvider.php

@@ -111,7 +111,7 @@ public function supportsClass($class)
      *
      * @return User
      */
-    private function loadUser($username, Entry $entry)
+    protected function loadUser($username, Entry $entry)
     {
         $password = $this->getPassword($entry);