[BUG] Fix the issue with deleting the "Host" header

[titxue]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Directly deleting the "Host" header causes the custom host in the requests plugin to fail.

Expected Behavior

The "Host" header should be customizable, rather than being restricted to the reverse proxy address.

Steps To Reproduce

1. Go to HttpProcess → Request → Rules → Headers.
2. Adding a custom Host value to the headers does not take effect.

Environment

ShenYu version(s):2.6.1

Debug logs

No response

Anything else?

The Host field is not set correctly when the upstream is a reverse proxy.

[moremind]

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