Move internal packages to an internal folder

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

internal/ui/logout.go

@@ -0,0 +1,40 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package ui // import "miniflux.app/v2/internal/ui"
+
+import (
+	"net/http"
+
+	"miniflux.app/v2/internal/config"
+	"miniflux.app/v2/internal/http/cookie"
+	"miniflux.app/v2/internal/http/request"
+	"miniflux.app/v2/internal/http/response/html"
+	"miniflux.app/v2/internal/http/route"
+	"miniflux.app/v2/internal/logger"
+	"miniflux.app/v2/internal/ui/session"
+)
+
+func (h *handler) logout(w http.ResponseWriter, r *http.Request) {
+	sess := session.New(h.store, request.SessionID(r))
+	user, err := h.store.UserByID(request.UserID(r))
+	if err != nil {
+		html.ServerError(w, r, err)
+		return
+	}
+
+	sess.SetLanguage(user.Language)
+	sess.SetTheme(user.Theme)
+
+	if err := h.store.RemoveUserSessionByToken(user.ID, request.UserSessionToken(r)); err != nil {
+		logger.Error("[UI:Logout] %v", err)
+	}
+
+	http.SetCookie(w, cookie.Expired(
+		cookie.CookieUserSessionID,
+		config.Opts.HTTPS,
+		config.Opts.BasePath(),
+	))
+
+	html.Redirect(w, r, route.Path(h.router, "login"))
+}