write client: apply custom headers before signing request #120

Job	Run time
fuzzing	0s
Build Prometheus for common architectures (0)	9m 47s
golangci-lint	3m 11s
Build Prometheus for all architectures	0s
Build Prometheus for common architectures (1)	9m 0s
Go tests	24m 59s
Build Prometheus for common architectures (2)	9m 23s
Go tests with previous Go version	8m 20s
Mixins tests	2m 25s
Go tests on Windows	9m 14s
UI tests	2m 27s
codeql / Analyze (go)	24m 38s
codeql / Analyze (javascript)	1m 54s
Publish UI on npm Registry	1m 17s
Publish main branch artifacts	0s
Publish release artefacts	0s
	1h 46m 35s

Provide feedback