minor #58094 Use Stringable whenever possible (fabpot)

This PR was merged into the 7.2 branch.

Discussion
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Use Stringable whenever possible

| Q             | A
| ------------- | ---
| Branch?       | 7.2
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Issues        | n/a
| License       | MIT

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Commits
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06b49968a5 Use Stringable whenever possible

Author: fabpot

Authenticator/FormLoginAuthenticator.php

@@ -133,15 +133,15 @@ private function getCredentials(Request $request): array
 
         $request->getSession()->set(SecurityRequestAttributes::LAST_USERNAME, $credentials['username']);
 
-        if (!\is_string($credentials['password']) && (!\is_object($credentials['password']) || !method_exists($credentials['password'], '__toString'))) {
+        if (!\is_string($credentials['password']) && !$credentials['password'] instanceof \Stringable) {
             throw new BadRequestHttpException(\sprintf('The key "%s" must be a string, "%s" given.', $this->options['password_parameter'], \gettype($credentials['password'])));
         }
 
         if ('' === (string) $credentials['password']) {
             throw new BadCredentialsException(\sprintf('The key "%s" must be a non-empty string.', $this->options['password_parameter']));
         }
 
-        if (!\is_string($credentials['csrf_token'] ?? '') && (!\is_object($credentials['csrf_token']) || !method_exists($credentials['csrf_token'], '__toString'))) {
+        if (!\is_string($credentials['csrf_token'] ?? '') && !$credentials['csrf_token'] instanceof \Stringable) {
             throw new BadRequestHttpException(\sprintf('The key "%s" must be a string, "%s" given.', $this->options['csrf_parameter'], \gettype($credentials['csrf_token'])));
         }