Support for Flutter 2.5.1

[kmaxion]

Hello,
Is there a plan to support Flutter 2.5.1 (using Dart 2.14) in the near future? Currently it's not compiling due to a difference in function signatures for HttpClient.authenticate

https://api.dart.dev/stable/2.14.2/dart-io/HttpClient/authenticate.html
https://github.com/openkraken/kraken/blob/main/kraken/lib/src/foundation/http_client.dart#L66-L69

使用的 Kraken 版本 ｜ What version of kraken are you using

Version 0.8.3+3

重现步骤 ｜ Steps To Reproduce

Run Flutter build on version 2.5.0 and above with Kraken as a dependency

预期结果 ｜ Expected results:
App should build and run

实际结果 ｜ Actual results:
Flutter app doesn't compile. Here is the error message:

/Users/user/.pub-cache/hosted/pub.dartlang.o rg/kraken-0.8.3+3/lib/src/foundation/http_client.dar t:68:37: Error: A value of type 'Future<bool> Function(Uri, String, String)?' can't be assigned to a variable of type 'Future<bool> Function(Uri, String, String?)?' because 'String?' is nullable and 'String' isn't. - 'Future' is from 'dart:async'. - 'Uri' is from 'dart:core'. nativeHttpClient.authenticate

[cnryb]

We are discussing how to support flutter 2.5.x .
Please pay attention to the detailed progress #700 .

[cnryb]

Support flutter 2.5.x in #817