Http constructor
Implementation
factory Http(String baseUrl,
{bool isInstance = true, BaseOptions? options, String? contentType}) {
var o = options ?? _baseOptions;
if (!isInstance) return Http._(o).._init(baseUrl);
if (instance == null) instance = Http._(o).._init(baseUrl);
if (contentType.en) instance!.options.contentType = contentType;
return instance!;
}