feat: M19 API audit log + M16a notifier connectors (Slack, Teams, PagerDuty, OpsGenie)

M19: HTTP middleware records every API call to the immutable audit trail
with method, path, actor, SHA-256 body hash, status, and latency. Best-effort
async recording via goroutine. Health/ready probes excluded.

M16a: Four pluggable notifier connectors — Slack (incoming webhook), Teams
(MessageCard), PagerDuty (Events API v2), OpsGenie (Alert API v2). Each
enabled by config env var. 30 new tests across middleware and connectors.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/connector/notifier/teams/teams.go

@@ -0,0 +1,93 @@
+package teams
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+)
+
+// Config holds configuration for the Microsoft Teams notifier.
+type Config struct {
+	// WebhookURL is the Teams incoming webhook URL.
+	WebhookURL string `json:"webhook_url"`
+}
+
+// Notifier sends notifications to Microsoft Teams via incoming webhooks.
+type Notifier struct {
+	config     Config
+	httpClient *http.Client
+}
+
+// New creates a new Teams notifier.
+func New(config Config) *Notifier {
+	return &Notifier{
+		config: config,
+		httpClient: &http.Client{
+			Timeout: 10 * time.Second,
+		},
+	}
+}
+
+// Channel returns the channel identifier.
+func (n *Notifier) Channel() string {
+	return "Teams"
+}
+
+// Send delivers a notification to Teams via webhook using MessageCard format.
+func (n *Notifier) Send(ctx context.Context, recipient string, subject string, body string) error {
+	card := teamsMessageCard{
+		Type:       "MessageCard",
+		Context:    "https://schema.org/extensions",
+		ThemeColor: "0076D7",
+		Summary:    subject,
+		Sections: []teamsSection{
+			{
+				ActivityTitle: subject,
+				Text:          body,
+				Markdown:      true,
+			},
+		},
+	}
+
+	jsonBytes, err := json.Marshal(card)
+	if err != nil {
+		return fmt.Errorf("teams: failed to marshal payload: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, n.config.WebhookURL, bytes.NewReader(jsonBytes))
+	if err != nil {
+		return fmt.Errorf("teams: failed to create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := n.httpClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("teams: request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		respBody, _ := io.ReadAll(resp.Body)
+		return fmt.Errorf("teams: webhook returned HTTP %d: %s", resp.StatusCode, string(respBody))
+	}
+
+	return nil
+}
+
+type teamsMessageCard struct {
+	Type       string         `json:"@type"`
+	Context    string         `json:"@context"`
+	ThemeColor string         `json:"themeColor"`
+	Summary    string         `json:"summary"`
+	Sections   []teamsSection `json:"sections"`
+}
+
+type teamsSection struct {
+	ActivityTitle string `json:"activityTitle"`
+	Text          string `json:"text"`
+	Markdown      bool   `json:"markdown"`
+}

internal/connector/notifier/teams/teams_test.go

@@ -0,0 +1,91 @@
+package teams
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestTeams_Channel(t *testing.T) {
+	n := New(Config{WebhookURL: "https://outlook.office.com/webhook/test"})
+	if n.Channel() != "Teams" {
+		t.Errorf("expected channel Teams, got %s", n.Channel())
+	}
+}
+
+func TestTeams_SendSuccess(t *testing.T) {
+	var receivedCard teamsMessageCard
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			t.Errorf("expected POST, got %s", r.Method)
+		}
+		if ct := r.Header.Get("Content-Type"); ct != "application/json" {
+			t.Errorf("expected application/json, got %s", ct)
+		}
+		if err := json.NewDecoder(r.Body).Decode(&receivedCard); err != nil {
+			t.Fatalf("failed to decode payload: %v", err)
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	n := New(Config{WebhookURL: server.URL})
+	err := n.Send(context.Background(), "team@example.com", "Renewal Failed", "Certificate mc-api-prod renewal failed after 3 attempts")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if receivedCard.Type != "MessageCard" {
+		t.Errorf("expected @type MessageCard, got %s", receivedCard.Type)
+	}
+	if receivedCard.Summary != "Renewal Failed" {
+		t.Errorf("expected summary 'Renewal Failed', got %s", receivedCard.Summary)
+	}
+	if receivedCard.ThemeColor != "0076D7" {
+		t.Errorf("expected theme color 0076D7, got %s", receivedCard.ThemeColor)
+	}
+	if len(receivedCard.Sections) != 1 {
+		t.Fatalf("expected 1 section, got %d", len(receivedCard.Sections))
+	}
+	if receivedCard.Sections[0].ActivityTitle != "Renewal Failed" {
+		t.Errorf("expected section title 'Renewal Failed', got %s", receivedCard.Sections[0].ActivityTitle)
+	}
+	if !strings.Contains(receivedCard.Sections[0].Text, "mc-api-prod") {
+		t.Errorf("expected body to contain cert ID, got %s", receivedCard.Sections[0].Text)
+	}
+	if !receivedCard.Sections[0].Markdown {
+		t.Error("expected markdown=true in section")
+	}
+}
+
+func TestTeams_SendHTTPError(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte("bad request"))
+	}))
+	defer server.Close()
+
+	n := New(Config{WebhookURL: server.URL})
+	err := n.Send(context.Background(), "", "Test", "body")
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !strings.Contains(err.Error(), "HTTP 400") {
+		t.Errorf("expected HTTP 400 in error, got %v", err)
+	}
+}
+
+func TestTeams_SendConnectionError(t *testing.T) {
+	n := New(Config{WebhookURL: "http://127.0.0.1:1"})
+	err := n.Send(context.Background(), "", "Test", "body")
+	if err == nil {
+		t.Fatal("expected connection error, got nil")
+	}
+	if !strings.Contains(err.Error(), "request failed") {
+		t.Errorf("expected 'request failed' in error, got %v", err)
+	}
+}