enhance(runner): add extra HTTP headers (#1269)

Add `runner.extra_headers` for reverse proxies that require request headers on the runner's API requests to Gitea, like registration, polling and log and status reports.

Headers the runner sets itself (authentication, User-Agent, protocol headers) stay authoritative. Extra headers are dropped when a redirect changes the hostname or leaves HTTPS, while the runner's own authentication headers follow redirects as before. Invalid or case-insensitively duplicated header names are rejected at config load.

Fixes: https://gitea.com/gitea/runner/issues/171
Co-authored-by: silverwind <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1269
Co-authored-by: bircni <[email protected]>

e2e/runner_harness.go

@@ -75,7 +75,7 @@ func startRunner(t *testing.T, repo, labelName string, options runnerOptions) *p
 	}
 	labelNames := []string{label.Name}
 
-	pingCli := client.New(fixture.baseURL, cfg.Runner.Insecure, "", "", config.RequestTimeout)
+	pingCli := client.New(fixture.baseURL, cfg.Runner.Insecure, "", "", config.RequestTimeout, cfg.Runner.ExtraHeaders)
 	if _, err := pingCli.Ping(ctx, connect.NewRequest(&pingv1.PingRequest{Data: t.Name()})); err != nil {
 		t.Fatalf("ping %s: %v", fixture.baseURL, err)
 	}
@@ -105,7 +105,7 @@ func startRunner(t *testing.T, repo, labelName string, options runnerOptions) *p
 		Ephemeral: regResp.Msg.Runner.Ephemeral,
 	}
 
-	cli := client.New(fixture.baseURL, cfg.Runner.Insecure, reg.UUID, reg.Token, config.RequestTimeout)
+	cli := client.New(fixture.baseURL, cfg.Runner.Insecure, reg.UUID, reg.Token, config.RequestTimeout, cfg.Runner.ExtraHeaders)
 
 	runner := run.NewRunner(cfg, reg, cli)
 	declResp, err := runner.Declare(ctx, labelNames)