Move internal packages to an internal folder

For reference: https://go.dev/doc/go1.4#internalpackages

internal/integration/pocket/pocket.go

@@ -0,0 +1,54 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package pocket // import "miniflux.app/v2/internal/integration/pocket"
+
+import (
+	"fmt"
+
+	"miniflux.app/v2/internal/http/client"
+)
+
+// Client represents a Pocket client.
+type Client struct {
+	consumerKey string
+	accessToken string
+}
+
+// NewClient returns a new Pocket client.
+func NewClient(consumerKey, accessToken string) *Client {
+	return &Client{consumerKey, accessToken}
+}
+
+// AddURL sends a single link to Pocket.
+func (c *Client) AddURL(link, title string) error {
+	if c.consumerKey == "" || c.accessToken == "" {
+		return fmt.Errorf("pocket: missing credentials")
+	}
+
+	type body struct {
+		AccessToken string `json:"access_token"`
+		ConsumerKey string `json:"consumer_key"`
+		Title       string `json:"title,omitempty"`
+		URL         string `json:"url"`
+	}
+
+	data := &body{
+		AccessToken: c.accessToken,
+		ConsumerKey: c.consumerKey,
+		Title:       title,
+		URL:         link,
+	}
+
+	clt := client.New("https://getpocket.com/v3/add")
+	response, err := clt.PostJSON(data)
+	if err != nil {
+		return fmt.Errorf("pocket: unable to send url: %v", err)
+	}
+
+	if response.HasServerFailure() {
+		return fmt.Errorf("pocket: unable to send url, status=%d", response.StatusCode)
+	}
+
+	return nil
+}