IdentityHandler: make getGuestIdentity() a regular interface method (BC break)

Promotes the optional @method to a required method, so User no longer needs method_exists() to call it. BC break: existing IdentityHandler implementations must now declare getGuestIdentity().

Author: dg

src/Security/IdentityHandler.php

@@ -10,7 +10,6 @@
 
 /**
  * Serializes and restores identity to/from persistent storage.
- * @method ?IIdentity getGuestIdentity()
  */
 interface IdentityHandler
 {
@@ -23,4 +22,9 @@ function sleepIdentity(IIdentity $identity): IIdentity;
 	 * Called after identity is read from storage. Typically refreshes roles or validates the token. Returns null to force logout.
 	 */
 	function wakeupIdentity(IIdentity $identity): ?IIdentity;
+
+	/**
+	 * Returns the identity for an anonymous (not logged-in) user, or null if none.
+	 */
+	function getGuestIdentity(): ?IIdentity;
 }

src/Security/User.php

@@ -178,7 +178,7 @@ private function resolveGuestIdentity(): ?IIdentity
 	{
 		if (!$this->guestIdentityResolved) {
 			$this->guestIdentityResolved = true;
-			$this->guestIdentity = $this->authenticator instanceof IdentityHandler && method_exists($this->authenticator, 'getGuestIdentity')
+			$this->guestIdentity = $this->authenticator instanceof IdentityHandler
 				? $this->authenticator->getGuestIdentity()
 				: null;
 		}