* Removing email field from the required arguments in comments

* Fixed gravatar and added database migration script

* Adding validation test cases for PostCommentParam

* Added unit test for PostCommentServiceImpl

* Address comments: removing identicon in gravatar, renaming migration script

* Address comment: removing gravata identicon from CommentProperties

* Address comments: Adding more unit tests for comment API

* Address comments: Adding integration tests for comment API

* 1.Add the lastBuildDate in RSS.
2.Add the updated in Atom.
3.Change the date format in RSS and Atom
4.Add the lastModified in the response header.

* fix code style

* Refactor application*.yml

* Remove application-user.yaml

* Fix invalid config for aspect

* Update gradle wrapper version

* Update spring boot version to 2.5.0-M2

* Fix wrong const of temp_dir

* Refactor error controller

* Fix startup error due to theme not found

* Refine error controller handler

* Refine multipart resolver config

* Fix ThemeRepositoryImplTest error

* Fix freemarker not found error

* chore: change jetty to undertow.

* Remove useless throws
Co-authored-by: Ryan Wang <i@ryanc.cc>

* feat: #1225

* fix: compatible with jdk1.8

* fix: format code

* fix: fix the problem that the status of the recycle bin file is incorrect when revocering

* fix: format code

* fix: format code

* fix: fix the post cannot be converted to recyling mode

* fix: post cannot be published on deleting the category password

* fix: fix jpa error

* fix: format code

* fix: encryption type extracted into enum

* fix: format code

* fix: format code

* fix: changes requested

* fix: format code

* fix: revert checkstyle.xml

* fix: change request

* fix: not encrypt 方法改为重载方法

* fix: 修复因调整 git 版本被回退的代码
Co-authored-by: Nxiangbei.yzx <xiangbei.yzx@alibaba-inc.com>

* Refactor checkstyle.xml and add .editorconfig

* Optimized imports

* Rearrange codes

* Fix check sytle error in source codes

* Reformat test codes

* Fix check style error in test codes

* Config checkstyle plugin

* Fix merge conflicts

* Update gradle wrapper version to 6.6.1

* Upgrade h2 version to 1.4.197

* Make controller log more details

* Refactor FileHandler

* Fix image reader error

* chore: remove redis cache store.

* chore: remove redis cache store.

* chore: update build.gradle.

* Update spring boot version and source compatibility version

* Rearrange some configs

* Upgrade swagger to 3.0.0

* Make swagger configurable

* Make swagger-ui.html path backward compatible

* Change jdk version into 11 in ci/cd scripts and Dockerfile