Move internal packages to an internal folder

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

internal/ui/category_save.go

@@ -0,0 +1,53 @@
+// 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/http/request"
+	"miniflux.app/v2/internal/http/response/html"
+	"miniflux.app/v2/internal/http/route"
+	"miniflux.app/v2/internal/logger"
+	"miniflux.app/v2/internal/model"
+	"miniflux.app/v2/internal/ui/form"
+	"miniflux.app/v2/internal/ui/session"
+	"miniflux.app/v2/internal/ui/view"
+	"miniflux.app/v2/internal/validator"
+)
+
+func (h *handler) saveCategory(w http.ResponseWriter, r *http.Request) {
+	loggedUser, err := h.store.UserByID(request.UserID(r))
+	if err != nil {
+		html.ServerError(w, r, err)
+		return
+	}
+
+	categoryForm := form.NewCategoryForm(r)
+
+	sess := session.New(h.store, request.SessionID(r))
+	view := view.New(h.tpl, r, sess)
+	view.Set("form", categoryForm)
+	view.Set("menu", "categories")
+	view.Set("user", loggedUser)
+	view.Set("countUnread", h.store.CountUnreadEntries(loggedUser.ID))
+	view.Set("countErrorFeeds", h.store.CountUserFeedsWithErrors(loggedUser.ID))
+
+	categoryRequest := &model.CategoryRequest{Title: categoryForm.Title}
+
+	if validationErr := validator.ValidateCategoryCreation(h.store, loggedUser.ID, categoryRequest); validationErr != nil {
+		view.Set("errorMessage", validationErr.TranslationKey)
+		html.OK(w, r, view.Render("create_category"))
+		return
+	}
+
+	if _, err = h.store.CreateCategory(loggedUser.ID, categoryRequest); err != nil {
+		logger.Error("[UI:SaveCategory] %v", err)
+		view.Set("errorMessage", "error.unable_to_create_category")
+		html.OK(w, r, view.Render("create_category"))
+		return
+	}
+
+	html.Redirect(w, r, route.Path(h.router, "categories"))
+}