Elastic Agent + Managing Fleet Behind Proxy

Hi,

We are connecting to fleet via proxy server, I am not sure how to send proxy certificates in the Proxy-Header CLI flag. Here is what I tried that did not work,

Elastic Version: 8.1

Request:

elastic-agent install -f --url="https://my-fleet-server:8220" --fleet-server-es=https://my-elastic-server:9200 --fleet-server-service-token=My-Token --fleet-server-policy=fleet-server-policy --fleet-server-insecure-http --proxy-url="https://my-proxy-server:443" --proxy-header={"proxy-cacert":"DigiCertCA.crt","proxy-cert":"SAT0000000.crt","proxy-key":"SAT0000000.key"}

Response:

{"log.level":"info","@timestamp":"2022-04-18T23:12:35.391-0700","log.origin":{"file.name":"cmd/enroll_cmd.go","file.line":727},"message":"Waiting for Elastic Agent to start","ecs.version":"1.6.0"}
{"log.level":"info","@timestamp":"2022-04-18T23:12:37.404-0700","log.origin":{"file.name":"cmd/enroll_cmd.go","file.line":777},"message":"Fleet Server - Starting","ecs.version":"1.6.0"}
{"log.level":"info","@timestamp":"2022-04-18T23:12:41.415-0700","log.origin":{"file.name":"cmd/enroll_cmd.go","file.line":777},"message":"Fleet Server - Error - Bad Request","ecs.version":"1.6.0"}

Ngnix Proxy log:

{"http.host":"my-elastic-server","http.url":"","http.version":"HTTP/1.1","http.status_code":"400","http.method":"CONNECT","http.referer":"","http.useragent":"Go-http-client/1.1","http.request":"CONNECT my-elastic-server:9200 HTTP/1.1","body_bytes_sent":"237","remote_addr":"104.27.197.12","remote_user":"","server.name":"~^iops. $","server.addr":"108.167.10.12","server.port":"443","ssl_client_cert":"","SSL_client_verify":"NONE","request_time":"0.000","response_content_type":"text/html","X-Forwarded-For":"104.24.17.2","server_name":"~^ihub-aiops. $","ssl_server_name":"proxy-poc-server.local","ssl_protocol":"TLSv1.3","ssl_curves":"X25519:prime256v1:secp384r1:secp521r1","ssl_client_fingerprint":"","ssl_cipher":"TLS_AES_256_GCM_SHA384"}

Note: On Proxy log, the ssl_clinet_cert is coming as NULL