feat: only allowed idps Disco support for SAML (needed for Beyond)

lib/Disco.php

@@ -292,6 +292,11 @@ class Disco extends PowerIdPDisco
             }
         }
 
+        if (!empty($this->originalsp[Disco::METADATA_ONLY_ALLOWED_IDPS])) {
+            $onlyAllowedIdps = $this->originalsp[Disco::METADATA_ONLY_ALLOWED_IDPS];
+            $onlyAllowedIdps = array_fill_keys($onlyAllowedIdps, 1);
+        }
+
         if ($this->processAarcIdpHintEnabled) {
             $hintedIdp = $this->processAarcIdpHint($this->state, $hintedIdp);
         }
@@ -310,7 +315,11 @@ class Disco extends PowerIdPDisco
             // either will throw an exception or redirect user, we can end prematurely
             return;
         } elseif (sizeof($idpList) === 1) {
-            Logger::info(self::DEBUG_PREFIX . 'Only one Idp left. Redirecting automatically. IdP: ' . $idpList[0]);
+            Logger::info(
+                self::DEBUG_PREFIX .
+                'Only one Idp left. Redirecting automatically. IdP: ' .
+                array_key_first($idpList)
+            );
             $idp = array_keys($idpList)[0];
             self::redirectToIdP($idp);
         }