* Contribute grafana/agent sigv4 code
* address review feedback
- move validation logic for RemoteWrite into unmarshal
- copy configuration fields from ec2 SD config
- remove enabled field, use pointer for enabling sigv4
* Update config/config.go
* Don't provide credentials if secret key / access key left blank
* Add SigV4 headers to the list of unchangeable headers.
* sigv4: don't include all headers in signature
* only test for equality in the authorization header, not the signed date
* address review feedback
1. s/httpClientConfigEnabled/httpClientConfigAuthEnabled
2. bearer_token tuples to "authorization"
3. Un-export NewSigV4RoundTripper
* add x-amz-content-sha256 to list of unchangeable headers
* Document sigv4 configuration
* add suggestion for using default AWS SDK credentials
Signed-off-by: Robert Fratto <robertfratto@gmail.com>
Co-authored-by: Julien Pivotto <roidelapluie@gmail.com>
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