RFR: 8368695: Support 101 switching protocol in jdk.httpserver [v5]

[Daniel Fuchs]

On Tue, 14 Oct 2025 17:34:09 GMT, Josiah Noel <duke at openjdk.org> wrote:

>> - adds a flag to ExchangeImpl to signal whether the current request is an Upgrade request
>> - Adds a new `UpgradeInputStream` to ensure that the server keeps track of when the upgraded request is closed
>> - on 101 response codes, `sendResponseHeaders` will not immediately close the output stream 
>> - on 101 response codes, `sendResponseHeaders` will use an `UndefLengthOutputStream`
>
> Josiah Noel has updated the pull request incrementally with one additional commit since the last revision:
> 
>   tab

Before going any further in the review I would like to see how this new feature would be documented. If we eventually decide to take it on board, then more extensive tests will be needed too.

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PR Comment: https://git.openjdk.org/jdk/pull/27751#issuecomment-3405626434