fix(integration): stop sending empty tags to Raindrop

strings.Split("", ",") returns [""], so an empty tag configuration
attached a single empty-string tag to every bookmark saved through the
Raindrop integration. Split the configured tags with SplitSeq, trim
whitespace, drop empty items, and omit the tags field entirely from the
payload when no tags are configured.

internal/integration/raindrop/raindrop.go

@@ -19,7 +19,13 @@ type Client struct {
 }
 
 func NewClient(token, collectionID, tags string) *Client {
-	return &Client{token: token, collectionID: collectionID, tags: strings.Split(tags, ",")}
+	var tagList []string
+	for tag := range strings.SplitSeq(tags, ",") {
+		if trimmedTag := strings.TrimSpace(tag); trimmedTag != "" {
+			tagList = append(tagList, trimmedTag)
+		}
+	}
+	return &Client{token: token, collectionID: collectionID, tags: tagList}
 }
 
 // https://developer.raindrop.io/v1/raindrops/single#create-raindrop
@@ -54,7 +60,7 @@ type raindrop struct {
 	Link       string     `json:"link"`
 	Title      string     `json:"title"`
 	Collection collection `json:"collection"`
-	Tags       []string   `json:"tags"`
+	Tags       []string   `json:"tags,omitempty"`
 }
 
 type collection struct {

internal/integration/raindrop/raindrop_test.go

@@ -0,0 +1,50 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package raindrop
+
+import (
+	"encoding/json"
+	"slices"
+	"testing"
+)
+
+func TestNewClientTagParsing(t *testing.T) {
+	tests := []struct {
+		name string
+		tags string
+		want []string
+	}{
+		{name: "empty string produces no tags", tags: "", want: nil},
+		{name: "single tag", tags: "news", want: []string{"news"}},
+		{name: "multiple tags", tags: "news,tech", want: []string{"news", "tech"}},
+		{name: "whitespace is trimmed", tags: " news , tech ", want: []string{"news", "tech"}},
+		{name: "empty items are dropped", tags: "news,,tech,", want: []string{"news", "tech"}},
+		{name: "only separators produce no tags", tags: ", ,", want: nil},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			client := NewClient("token", "collection", tt.tags)
+			if !slices.Equal(client.tags, tt.want) {
+				t.Errorf("NewClient(%q) tags = %#v, want %#v", tt.tags, client.tags, tt.want)
+			}
+		})
+	}
+}
+
+func TestPayloadOmitsEmptyTags(t *testing.T) {
+	payload, err := json.Marshal(&raindrop{Link: "https://example.com", Title: "Example"})
+	if err != nil {
+		t.Fatalf("unable to marshal payload: %v", err)
+	}
+
+	var fields map[string]json.RawMessage
+	if err := json.Unmarshal(payload, &fields); err != nil {
+		t.Fatalf("unable to unmarshal payload: %v", err)
+	}
+
+	if _, found := fields["tags"]; found {
+		t.Errorf("payload without tags should omit the tags field, got %s", payload)
+	}
+}