resolve #8562

Creating new URLSession for every request isn't optimal and it is not recommended by Apple.
Also, NSPOSIXErrorDomain Code=28 "No space left on device" will get thrown after too many URLSessions get created.

https://developer.apple.com/videos/play/wwdc2018/714/?time=1646
https://developer.apple.com/videos/play/wwdc2017/709/
https://developer.apple.com/forums/thread/84663
https://stackoverflow.com/questions/67318867/error-domain-nsposixerrordomain-code-28-no-space-left-on-device-userinfo-kcf/67507327#67507327

I've hashed the session's configuration, credentials and sessionDelegate with Hasher so we can reuse URLSessions with the same settings.

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