fix(db): use `caching_sha2_password` for MySQL

`caching_sha2_password` was added in 8.0.4 as the default
authentication plugin. `mysql_native_password` is deprecated since then.
In MySQL 8.4 it was disabled by default so a user need to manually
reenable it to make it work.
In MySQL 9.0 it is removed and causes the following error:

> SQLSTATE[HY000] [1524] Plugin 'mysql_native_password' is not loaded

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

lib/private/Setup/MySQL.php

@@ -8,6 +8,7 @@
 namespace OC\Setup;
 
 use Doctrine\DBAL\Platforms\MySQL80Platform;
+use Doctrine\DBAL\Platforms\MySQL84Platform;
 use OC\DB\ConnectionAdapter;
 use OC\DB\MySqlTools;
 use OCP\IDBConnection;
@@ -92,22 +93,29 @@ class MySQL extends AbstractDatabase {
 	 * @throws \OC\DatabaseSetupException
 	 */
 	private function createDBUser($connection): void {
+		$name = $this->dbUser;
+		$password = $this->dbPassword;
+
 		try {
-			$name = $this->dbUser;
-			$password = $this->dbPassword;
 			// we need to create 2 accounts, one for global use and one for local user. if we don't specify the local one,
 			// the anonymous user would take precedence when there is one.
 
-			if ($connection->getDatabasePlatform() instanceof Mysql80Platform) {
+			if ($connection->getDatabasePlatform() instanceof MySQL84Platform) {
+				$query = "CREATE USER ?@'localhost' IDENTIFIED WITH caching_sha2_password BY ?";
+				$connection->executeStatement($query, [$name,$password]);
+				$query = "CREATE USER ?@'%' IDENTIFIED WITH caching_sha2_password BY ?";
+				$connection->executeStatement($query, [$name,$password]);
+			} elseif ($connection->getDatabasePlatform() instanceof Mysql80Platform) {
+				// TODO: Remove this elseif section as soon as MySQL 8.0 is out-of-support (after April 2026)
 				$query = "CREATE USER ?@'localhost' IDENTIFIED WITH mysql_native_password BY ?";
-				$connection->executeUpdate($query, [$name,$password]);
+				$connection->executeStatement($query, [$name,$password]);
 				$query = "CREATE USER ?@'%' IDENTIFIED WITH mysql_native_password BY ?";
-				$connection->executeUpdate($query, [$name,$password]);
+				$connection->executeStatement($query, [$name,$password]);
 			} else {
 				$query = "CREATE USER ?@'localhost' IDENTIFIED BY ?";
-				$connection->executeUpdate($query, [$name,$password]);
+				$connection->executeStatement($query, [$name,$password]);
 				$query = "CREATE USER ?@'%' IDENTIFIED BY ?";
-				$connection->executeUpdate($query, [$name,$password]);
+				$connection->executeStatement($query, [$name,$password]);
 			}
 		} catch (\Exception $ex) {
 			$this->logger->error('Database user creation failed.', [
@@ -158,6 +166,11 @@ class MySQL extends AbstractDatabase {
 						//use the admin login data for the new database user
 						$this->dbUser = $adminUser;
 						$this->createDBUser($connection);
+						// if sharding is used we need to manually call this for every shard as those also need the user setup!
+						/** @var ConnectionAdapter $connection */
+						foreach ($connection->getInner()->getShardConnections() as $shard) {
+							$this->createDBUser($shard);
+						}
 
 						break;
 					} else {