Hook execution fails with response streaming enabled if connection is abandoned by client

[dikderoy]

Command execution stops with signal: broken pipe if the connection is abandoned/interrupted while the script is still executing

[dikderoy]

need to track and suppress future writes & flushes on err here:

ci-webhook/internal/handler/handler.go

Lines 89 to 95 in ad8f1bd

	func (fw *flushWriter) Write(p []byte) (n int, err error) {
	n, err = fw.w.Write(p)
	if n > 0 {
	fw.w.Flush()
	}
	return
	}