enhance: trust a private CA with runner.ca_file and add container.volumes (#1366)

Adds `container.volumes`, mounted into every Docker job, service and action container. Sources are paths on the Docker daemon's host and need no `valid_volumes` entry, and workflow volumes may use them only with the same access.

Adds `runner.ca_file`, a private CA trusted for the Gitea instance besides the system's by the runner's connections and its artifact proxy. Runner-side git and `builtin:checkout` use it as their CA bundle for the instance, persisted with the checkout's credentials. Jobs get it at `/var/run/act/ca.crt` with `NODE_EXTRA_CA_CERTS` pointing there unless the job or its image sets it. Git in jobs, as run by `actions/checkout`, needs the CA in the image's bundle, for example through `container.volumes`.

Fixes: https://gitea.com/gitea/runner/issues/568
Fixes: https://gitea.com/gitea/runner/issues/671
Co-authored-by: silverwind <[email protected]>
Co-authored-by: silverwind <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1366
Reviewed-by: silverwind <[email protected]>
Co-authored-by: bircni <[email protected]>

act/artifactcache/handler.go

@@ -104,7 +104,8 @@ type Handler struct {
 	stopSync context.CancelFunc
 	syncing  sync.WaitGroup
 
-	outboundIP string
+	outboundIP        string
+	instanceTransport http.RoundTripper
 
 	// internalSecret guards /_internal/{register,revoke}. When set, a remote
 	// runner can use these endpoints to pre-register per-job
@@ -143,19 +144,21 @@ type Options struct {
 	// in-process RegisterJob method directly.
 	InternalSecret string
 
-	Policy Policy
-	Logger *logging.Logger
+	Policy            Policy
+	Logger            *logging.Logger
+	InstanceTransport http.RoundTripper // reaches the instance artifact requests are forwarded to, nil for http.DefaultTransport
 }
 
 // StartHandler starts an embedded cache or forwards cache requests to Upstream.
 func StartHandler(opts Options) (*Handler, error) {
 	dir, logger := opts.Dir, opts.Logger
 	h := &Handler{
-		creds:          make(map[string]*credEntry),
-		internalSecret: opts.InternalSecret,
-		policy:         opts.Policy.withDefaults(),
-		freeDisk:       disk.FreeBytes,
-		dbLock:         make(chan struct{}, 1),
+		creds:             make(map[string]*credEntry),
+		internalSecret:    opts.InternalSecret,
+		policy:            opts.Policy.withDefaults(),
+		freeDisk:          disk.FreeBytes,
+		dbLock:            make(chan struct{}, 1),
+		instanceTransport: opts.InstanceTransport,
 	}
 
 	if logger == nil {