Move internal packages to an internal folder

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

internal/model/entry.go

@@ -0,0 +1,49 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package model // import "miniflux.app/v2/internal/model"
+
+import (
+	"time"
+)
+
+// Entry statuses and default sorting order.
+const (
+	EntryStatusUnread       = "unread"
+	EntryStatusRead         = "read"
+	EntryStatusRemoved      = "removed"
+	DefaultSortingOrder     = "published_at"
+	DefaultSortingDirection = "asc"
+)
+
+// Entry represents a feed item in the system.
+type Entry struct {
+	ID          int64         `json:"id"`
+	UserID      int64         `json:"user_id"`
+	FeedID      int64         `json:"feed_id"`
+	Status      string        `json:"status"`
+	Hash        string        `json:"hash"`
+	Title       string        `json:"title"`
+	URL         string        `json:"url"`
+	CommentsURL string        `json:"comments_url"`
+	Date        time.Time     `json:"published_at"`
+	CreatedAt   time.Time     `json:"created_at"`
+	ChangedAt   time.Time     `json:"changed_at"`
+	Content     string        `json:"content"`
+	Author      string        `json:"author"`
+	ShareCode   string        `json:"share_code"`
+	Starred     bool          `json:"starred"`
+	ReadingTime int           `json:"reading_time"`
+	Enclosures  EnclosureList `json:"enclosures"`
+	Feed        *Feed         `json:"feed,omitempty"`
+	Tags        []string      `json:"tags"`
+}
+
+// Entries represents a list of entries.
+type Entries []*Entry
+
+// EntriesStatusUpdateRequest represents a request to change entries status.
+type EntriesStatusUpdateRequest struct {
+	EntryIDs []int64 `json:"entry_ids"`
+	Status   string  `json:"status"`
+}