better comment the elaticsearch api endpoint

Author: robin-moser

internal/notif/elasticsearch/client.go

@@ -82,13 +82,15 @@ func (c *Client) Send(entry model.NotifEntry) error {
 		return err
 	}
 
-	// Create Elasticsearch URL
+	// Build the Elasticsearch indexing URL
+	// This uses the Index API (POST /{index}/_doc) to create a document with an auto-generated _id:
+	// https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-create
 	url := fmt.Sprintf("%s://%s:%d/%s/_doc", c.cfg.Scheme, c.cfg.Host, c.cfg.Port, c.cfg.Index)
 
 	cancelCtx, cancel := context.WithCancelCause(context.Background())
 	timeoutCtx, _ := context.WithTimeoutCause(cancelCtx, *c.cfg.Timeout, errors.WithStack(context.DeadlineExceeded)) //nolint:govet // no need to manually cancel this context as we already rely on parent
 	defer func() { cancel(errors.WithStack(context.Canceled)) }()
-	
+
 	hc := http.Client{
 		Transport: &http.Transport{
 			TLSClientConfig: &tls.Config{