merged branch davedevelopment/duplicate-auth-providers (PR #673)

This PR was merged into the master branch.

Discussion
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Only register one of each authentication provider

Fixes #655

Commits
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657bf5f6 Only register one of each authentication provider

src/Silex/Provider/SecurityServiceProvider.php

@@ -241,7 +241,7 @@ class SecurityServiceProvider implements ServiceProviderInterface
 
             $app['security.authentication_providers'] = array_map(function ($provider) use ($app) {
                 return $app[$provider];
-            }, $providers);
+            }, array_unique($providers));
 
             $map = new FirewallMap();
             foreach ($configs as $name => $config) {