Move internal packages to an internal folder

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

reader/opml/handler.go

@@ -1,93 +0,0 @@
-// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
-// SPDX-License-Identifier: Apache-2.0
-
-package opml // import "miniflux.app/v2/reader/opml"
-
-import (
-	"errors"
-	"fmt"
-	"io"
-
-	"miniflux.app/v2/logger"
-	"miniflux.app/v2/model"
-	"miniflux.app/v2/storage"
-)
-
-// Handler handles the logic for OPML import/export.
-type Handler struct {
-	store *storage.Storage
-}
-
-// Export exports user feeds to OPML.
-func (h *Handler) Export(userID int64) (string, error) {
-	feeds, err := h.store.Feeds(userID)
-	if err != nil {
-		return "", err
-	}
-
-	var subscriptions SubcriptionList
-	for _, feed := range feeds {
-		subscriptions = append(subscriptions, &Subcription{
-			Title:        feed.Title,
-			FeedURL:      feed.FeedURL,
-			SiteURL:      feed.SiteURL,
-			CategoryName: feed.Category.Title,
-		})
-	}
-
-	return Serialize(subscriptions), nil
-}
-
-// Import parses and create feeds from an OPML import.
-func (h *Handler) Import(userID int64, data io.Reader) error {
-	subscriptions, err := Parse(data)
-	if err != nil {
-		return err
-	}
-
-	for _, subscription := range subscriptions {
-		if !h.store.FeedURLExists(userID, subscription.FeedURL) {
-			var category *model.Category
-			var err error
-
-			if subscription.CategoryName == "" {
-				category, err = h.store.FirstCategory(userID)
-				if err != nil {
-					logger.Error("[OPML:Import] %v", err)
-					return errors.New("unable to find first category")
-				}
-			} else {
-				category, err = h.store.CategoryByTitle(userID, subscription.CategoryName)
-				if err != nil {
-					logger.Error("[OPML:Import] %v", err)
-					return errors.New("unable to search category by title")
-				}
-
-				if category == nil {
-					category, err = h.store.CreateCategory(userID, &model.CategoryRequest{Title: subscription.CategoryName})
-					if err != nil {
-						logger.Error("[OPML:Import] %v", err)
-						return fmt.Errorf(`unable to create this category: %q`, subscription.CategoryName)
-					}
-				}
-			}
-
-			feed := &model.Feed{
-				UserID:   userID,
-				Title:    subscription.Title,
-				FeedURL:  subscription.FeedURL,
-				SiteURL:  subscription.SiteURL,
-				Category: category,
-			}
-
-			h.store.CreateFeed(feed)
-		}
-	}
-
-	return nil
-}
-
-// NewHandler creates a new handler for OPML files.
-func NewHandler(store *storage.Storage) *Handler {
-	return &Handler{store: store}
-}