add simple webhook feature for peer, interface and user events (#398)

internal/app/webhooks/model.go

@@ -0,0 +1,48 @@
+package webhooks
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+)
+
+// WebhookData is the data structure for the webhook payload.
+type WebhookData struct {
+	// Event is the event type (e.g. create, update, delete)
+	Event WebhookEvent `json:"event" example:"create"`
+
+	// Entity is the entity type (e.g. user, peer, interface)
+	Entity WebhookEntity `json:"entity" example:"user"`
+
+	// Identifier is the identifier of the entity
+	Identifier string `json:"identifier" example:"user-123"`
+
+	// Payload is the payload of the event
+	Payload any `json:"payload"`
+}
+
+// Serialize serializes the WebhookData to JSON and returns it as an io.Reader.
+func (d *WebhookData) Serialize() (io.Reader, error) {
+	data, err := json.Marshal(d)
+	if err != nil {
+		return nil, err
+	}
+
+	return bytes.NewReader(data), nil
+}
+
+type WebhookEntity = string
+
+const (
+	WebhookEntityUser      WebhookEntity = "user"
+	WebhookEntityPeer      WebhookEntity = "peer"
+	WebhookEntityInterface WebhookEntity = "interface"
+)
+
+type WebhookEvent = string
+
+const (
+	WebhookEventCreate WebhookEvent = "create"
+	WebhookEventUpdate WebhookEvent = "update"
+	WebhookEventDelete WebhookEvent = "delete"
+)