[ahmadreza-fatemikia]

DatabaseManager::connection(), purge(), disconnect(), reconnect() and usingConnection() all accept enums, but setDefaultConnection() stores the given value in the configuration as-is. When it receives an enum, the enum instance is written to database.default, and every subsequent query on the default connection fails:

enum Connection: string
{
    case Reporting = 'reporting';
}

DB::setDefaultConnection(Connection::Reporting);

DB::table('users')->get();
// TypeError: str_ends_with(): Argument #1 ($haystack) must be of type string, Connection given

This PR normalizes the name using enum_value(), matching the setDefaultDriver() methods of the other managers (AuthManager, CacheManager, MailManager, QueueManager, LogManager, etc.), and adds tests for both backed and unit enums.