feat(dbal): add proper insert ignore conflict method for MySQL

Signed-off-by: Benjamin Gaussorgues <benjamin.gaussorgues@nextcloud.com>

lib/private/DB/AdapterMySQL.php

@@ -35,4 +35,20 @@ protected function getCollation(): string {
 
 		return $this->collation;
 	}
+
+	public function insertIgnoreConflict(string $table, array $values) : int {
+		$builder = $this->conn->getQueryBuilder();
+		$builder->insert($table);
+		$updates = [];
+		foreach ($values as $key => $value) {
+			$builder->setValue($key, $builder->createNamedParameter($value));
+			$updates[] = "`$key`=VALUES(`$key`)";
+		}
+
+		return $this->conn->executeStatement(
+			$builder->getSQL() . ' ON DUPLICATE KEY UPDATE '.implode(',', $updates),
+			$builder->getParameters(),
+			$builder->getParameterTypes()
+		);
+	}
 }