Refactor rename user and rename organization (#24052)

This PR is a refactor at the beginning. And now it did 4 things.
- [x] Move renaming organizaiton and user logics into services layer and
merged as one function
- [x] Support rename a user capitalization only. For example, rename the
user from `Lunny` to `lunny`. We just need to change one table `user`
and others should not be touched.
- [x] Before this PR, some renaming were missed like `agit`
- [x] Fix bug the API reutrned from `http.StatusNoContent` to `http.StatusOK`

services/user/avatar.go

@@ -0,0 +1,62 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package user
+
+import (
+	"fmt"
+	"io"
+
+	"code.gitea.io/gitea/models/db"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/avatar"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/storage"
+)
+
+// UploadAvatar saves custom avatar for user.
+func UploadAvatar(u *user_model.User, data []byte) error {
+	avatarData, err := avatar.ProcessAvatarImage(data)
+	if err != nil {
+		return err
+	}
+
+	ctx, committer, err := db.TxContext(db.DefaultContext)
+	if err != nil {
+		return err
+	}
+	defer committer.Close()
+
+	u.UseCustomAvatar = true
+	u.Avatar = avatar.HashAvatar(u.ID, data)
+	if err = user_model.UpdateUserCols(ctx, u, "use_custom_avatar", "avatar"); err != nil {
+		return fmt.Errorf("updateUser: %w", err)
+	}
+
+	if err := storage.SaveFrom(storage.Avatars, u.CustomAvatarRelativePath(), func(w io.Writer) error {
+		_, err := w.Write(avatarData)
+		return err
+	}); err != nil {
+		return fmt.Errorf("Failed to create dir %s: %w", u.CustomAvatarRelativePath(), err)
+	}
+
+	return committer.Commit()
+}
+
+// DeleteAvatar deletes the user's custom avatar.
+func DeleteAvatar(u *user_model.User) error {
+	aPath := u.CustomAvatarRelativePath()
+	log.Trace("DeleteAvatar[%d]: %s", u.ID, aPath)
+	if len(u.Avatar) > 0 {
+		if err := storage.Avatars.Delete(aPath); err != nil {
+			return fmt.Errorf("Failed to remove %s: %w", aPath, err)
+		}
+	}
+
+	u.UseCustomAvatar = false
+	u.Avatar = ""
+	if _, err := db.GetEngine(db.DefaultContext).ID(u.ID).Cols("avatar, use_custom_avatar").Update(u); err != nil {
+		return fmt.Errorf("UpdateUser: %w", err)
+	}
+	return nil
+}