notification: payload + Channel interface

internal/notification/channel.go

@@ -0,0 +1,20 @@
+package notification
+
+import (
+	"context"
+	"time"
+)
+
+// Channel is the per-kind transport. Implementations live in
+// webhook.go / ntfy.go / smtp.go. Send must respect ctx (5s for HTTP,
+// 10s for SMTP) and never panic.
+type Channel interface {
+	// Kind returns the kind string ("webhook", "ntfy", "smtp"). Used
+	// for log enrichment and dispatcher routing.
+	Kind() string
+
+	// Send delivers one payload. Returns (statusCode, latency, err).
+	// statusCode is HTTP for HTTP channels, the SMTP final-line code
+	// (e.g. 250) for SMTP, 0 if the call didn't reach a wire response.
+	Send(ctx context.Context, p Payload) (statusCode int, latency time.Duration, err error)
+}

internal/notification/payload.go

@@ -0,0 +1,36 @@
+// Package notification owns the fan-out of alert events to operator-
+// configured channels. Three channels in v1: webhook, ntfy, smtp.
+// Each channel implements Channel.Send for one Payload at a time;
+// the Hub orchestrates fan-out, persists to notification_log.
+package notification
+
+import "time"
+
+// Event identifies the lifecycle hook this notification is for.
+type Event string
+
+const (
+	// EventRaised occurs when an alert is first raised.
+	EventRaised Event = "alert.raised"
+	// EventAcknowledged occurs when an alert is acknowledged.
+	EventAcknowledged Event = "alert.acknowledged"
+	// EventResolved occurs when an alert is resolved.
+	EventResolved Event = "alert.resolved"
+	// EventTest is used for test notifications.
+	EventTest Event = "alert.test"
+)
+
+// Payload is the per-event blob every channel renders into its own
+// shape. Severity maps to channel-specific priority (ntfy) or stays
+// in the body (webhook/smtp).
+type Payload struct {
+	Event    Event  // alert.raised | … | alert.test
+	AlertID  string // ULID
+	Severity string // info | warning | critical
+	Kind     string // backup_failed | …
+	HostID   string
+	HostName string
+	Message  string
+	RaisedAt time.Time
+	Link     string // Absolute URL to /alerts/<id>; built by Hub
+}