Initial commit: RMM Agent + Backend

- Go Agent (FreeBSD/amd64) fuer OPNsense
- Go Backend (Linux/amd64) mit REST API + SQLite
- Collector: Hardware, CPU, Memory, Disks, Network, Services,
  WireGuard, DHCP (KEA/ISC/dnsmasq), Routes, Gateways,
  Certificates, Plugins, Updates
- Persistente Agent-ID
- TLS + API-Key Auth
- WebSocket-Infrastruktur (WIP): bidirektionaler Command-Kanal,
  TCP-Tunnel fuer Remote-Zugriff auf Firewall-WebUI
- Lastenheft und README

agent/client/client.go

@@ -0,0 +1,95 @@
+package client
+
+import (
+	"bytes"
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+)
+
+type Client struct {
+	baseURL    string
+	apiKey     string
+	httpClient *http.Client
+}
+
+func New(baseURL, apiKey string, insecure bool) *Client {
+	transport := &http.Transport{
+		TLSClientConfig: &tls.Config{
+			InsecureSkipVerify: insecure,
+		},
+	}
+
+	return &Client{
+		baseURL: baseURL,
+		apiKey:  apiKey,
+		httpClient: &http.Client{
+			Transport: transport,
+			Timeout:   30 * time.Second,
+		},
+	}
+}
+
+// Register - Agent am Backend registrieren, gibt Agent-ID zurueck
+func (c *Client) Register(req interface{}) (string, error) {
+	body, err := json.Marshal(req)
+	if err != nil {
+		return "", err
+	}
+
+	resp, err := c.doRequest("POST", "/api/v1/agent/register", body)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	respBody, _ := io.ReadAll(resp.Body)
+
+	if resp.StatusCode != http.StatusCreated {
+		return "", fmt.Errorf("Registrierung fehlgeschlagen (HTTP %d): %s", resp.StatusCode, string(respBody))
+	}
+
+	var result struct {
+		ID string `json:"id"`
+	}
+	if err := json.Unmarshal(respBody, &result); err != nil {
+		return "", fmt.Errorf("Response parsen: %w", err)
+	}
+
+	return result.ID, nil
+}
+
+// Heartbeat - Systemdaten an Backend senden
+func (c *Client) Heartbeat(req interface{}) error {
+	body, err := json.Marshal(req)
+	if err != nil {
+		return err
+	}
+
+	resp, err := c.doRequest("POST", "/api/v1/agent/heartbeat", body)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		respBody, _ := io.ReadAll(resp.Body)
+		return fmt.Errorf("Heartbeat fehlgeschlagen (HTTP %d): %s", resp.StatusCode, string(respBody))
+	}
+
+	return nil
+}
+
+func (c *Client) doRequest(method, path string, body []byte) (*http.Response, error) {
+	req, err := http.NewRequest(method, c.baseURL+path, bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-API-Key", c.apiKey)
+
+	return c.httpClient.Do(req)
+}