feat: Implement configuration management and DNS provider integration

- Added configuration management using Viper in internal/config/config.go
- Implemented ClientConfig, ServerConfig, TLSConfig, HetznerConfig, UpstreamConfig, and main Config struct.
- Created LoadConfig function to read and validate configuration files.
- Developed Hetzner DNS provider in internal/provider/hetzner/hetzner.go with methods for updating DNS records.
- Added comprehensive unit tests for configuration loading and Hetzner provider functionality.
- Established HTTP server with metrics and update endpoint in internal/server/server.go.
- Implemented request handling, authorization, and error management in the server.
- Created integration tests for the Hetzner provider API interactions.
- Removed legacy dynamic DNS integration tests in favor of the new API-based approach.

internal/server/server_router_test.go

@@ -0,0 +1,105 @@
+package server_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"git.cloonar.com/cloonar/updns/internal/config"
+	"git.cloonar.com/cloonar/updns/internal/server"
+)
+
+func newTestConfig(provider string) *config.Config {
+	return &config.Config{
+		Server: config.ServerConfig{
+			BindAddress: ":0",
+			TLS:         config.TLSConfig{Enabled: false},
+		},
+		Upstream: config.UpstreamConfig{
+			Provider: provider,
+			Hetzner:  config.HetznerConfig{APIToken: "token"},
+		},
+		Clients: map[string]config.ClientConfig{
+			"client1": {
+				Secret:   "s3cr3t",
+				Exact:    []string{"a.example.com"},
+				Wildcard: []string{"example.net"},
+			},
+		},
+	}
+}
+
+func TestMetricsEndpoint(t *testing.T) {
+	r := server.NewRouter(newTestConfig("unknown"))
+	req := httptest.NewRequest("GET", "/metrics", nil)
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200 OK, got %d", w.Code)
+	}
+}
+
+func TestUpdateInvalidJSON(t *testing.T) {
+	r := server.NewRouter(newTestConfig("unknown"))
+	req := httptest.NewRequest("POST", "/update", bytes.NewBufferString("{invalid"))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400 BadRequest, got %d", w.Code)
+	}
+}
+
+func TestUpdateUnauthorizedKey(t *testing.T) {
+	r := server.NewRouter(newTestConfig("unknown"))
+	body := map[string]string{"key": "bad", "secret": "x", "host": "a.example.com"}
+	data, _ := json.Marshal(body)
+	req := httptest.NewRequest("POST", "/update", bytes.NewBuffer(data))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusUnauthorized {
+		t.Errorf("expected 401 Unauthorized, got %d", w.Code)
+	}
+}
+
+func TestUpdateHostForbidden(t *testing.T) {
+	r := server.NewRouter(newTestConfig("unknown"))
+	body := map[string]string{"key": "client1", "secret": "s3cr3t", "host": "bad.example.com"}
+	data, _ := json.Marshal(body)
+	req := httptest.NewRequest("POST", "/update", bytes.NewBuffer(data))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusForbidden {
+		t.Errorf("expected 403 Forbidden, got %d", w.Code)
+	}
+}
+
+func TestUpdateProviderNotConfigured(t *testing.T) {
+	r := server.NewRouter(newTestConfig("unknown"))
+	body := map[string]string{"key": "client1", "secret": "s3cr3t", "host": "a.example.com"}
+	data, _ := json.Marshal(body)
+	req := httptest.NewRequest("POST", "/update", bytes.NewBuffer(data))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("expected 500 InternalServerError, got %d", w.Code)
+	}
+}
+
+func TestUpdateSuccess(t *testing.T) {
+	r := server.NewRouter(newTestConfig("hetzner"))
+	body := map[string]string{"key": "client1", "secret": "s3cr3t", "host": "a.example.com", "ip": "1.2.3.4"}
+	data, _ := json.Marshal(body)
+	req := httptest.NewRequest("POST", "/update", bytes.NewBuffer(data))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200 OK, got %d", w.Code)
+	}
+}