feat(docker): add Docker socket proxy support and related configurations

- Introduced Docker socket proxy handling in the agent.
- Added environment variables for Docker socket configuration.
- Implemented new Docker handler with endpoint permissions based on environment settings.
- Added tests for Docker handler functionality.
- Updated go.mod to include gorilla/mux for routing.

agent/pkg/handler/docker_socket.go

@@ -16,6 +16,13 @@ func serviceUnavailable(w http.ResponseWriter, r *http.Request) {
 	http.Error(w, "docker socket is not available", http.StatusServiceUnavailable)
 }
 
+func mockDockerSocketHandler() http.HandlerFunc {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("mock docker response"))
+	})
+}
+
 func DockerSocketHandler() http.HandlerFunc {
 	dockerClient, err := docker.NewClient(common.DockerHostFromEnv)
 	if err != nil {