feat: allow unregistering group backends

Signed-off-by: Robin Appelman <robin@icewind.nl>

Author: icewind1991

lib/private/Group/Manager.php

@@ -103,6 +103,14 @@ public function addBackend($backend) {
 		$this->clearCaches();
 	}
 
+	#[\Override]
+	public function removeBackend(GroupInterface $backend): void {
+		$this->clearCaches();
+		if (($i = array_search($backend, $this->backends)) !== false) {
+			unset($this->backends[$i]);
+		}
+	}
+
 	#[\Override]
 	public function clearBackends() {
 		$this->backends = [];

lib/public/IGroupManager.php

@@ -38,6 +38,11 @@ public function isBackendUsed($backendClass);
 	 */
 	public function addBackend($backend);
 
+	/**
+	 * @since 34.0.0
+	 */
+	public function removeBackend(GroupInterface $backend): void;
+
 	/**
 	 * @since 8.0.0
 	 */