#### What type of PR is this?
/kind feature
/milestone 2.10.x
/area core
#### What this PR does / why we need it:
新增消息和通知机制的实现
how to test it?
1. 执行以下命令配置发件服务
```shell
curl -u admin:admin -X POST 'http://localhost:8090/apis/api.console.halo.run/v1alpha1/notifiers/default-email-notifier/senderConfig' \
--header 'Content-Type: application/json' \
--data-raw '{
"displayName": "Halo Team",
"username": "{发件使用的邮箱}",
"password": "{发件邮箱密码}",
"host": "smtp.exmail.qq.com",
"port": "587"
}'
```
2. 评论文章或页面可以收到通知
3. 文章/页面作者是评论者不发送新评论通知，回复者是评论作者不发送回复通知
#### Which issue(s) this PR fixes:
Fixes#4045
#### Does this PR introduce a user-facing change?
```release-note
新增消息和通知机制的实现
```
#### What type of PR is this?
/kind feature
/kind api-change
/area core
#### What this PR does / why we need it:
Support for personal access token mechanism.
#### Which issue(s) this PR fixes:
Fixes https://github.com/halo-dev/halo/issues/1309
#### Special notes for your reviewer:
#### Does this PR introduce a user-facing change?
```release-note
提供个人访问令牌机制
```
#### What type of PR is this?
/kind feature
/area core
/milestone 2.7.x
#### What this PR does / why we need it:
Refactor configuration properties to configure caching with separate names, so that we can enable / disable cache with name.
#### Which issue(s) this PR fixes:
Fixes https://github.com/halo-dev/halo/issues/4144
#### Does this PR introduce a user-facing change?
```release-note
None
```
#### What type of PR is this?
/kind feature
/milestone 2.7.x
/area core
#### What this PR does / why we need it:
为主题端的文章和自定义页面内容添加扩展点
插件可以通过实现扩展点来干预文章和自定义页面的内容显示，如修改内容的 html 结构，改变特定样式等
使用方式参考：[docs/extension-points/content.md](9b2b9f1837)
#### Which issue(s) this PR fixes:
Fixes#4003
#### Does this PR introduce a user-facing change?
```release-note
为主题端的文章和自定义页面内容添加扩展点
```
#### What type of PR is this?
/kind feature
/area core
#### What this PR does / why we need it:
This PR adds dependency [spring-boot-starter-cache](https://docs.spring.io/spring-boot/docs/current/reference/html/io.html#io.caching) as cache framework and [caffeine](https://github.com/ben-manes/caffeine/wiki) as cache implementation to cache template rendering result.
By default, we disable the cache feature. If you want to enable it, please try to configure properties like this:
```yaml
halo:
cache:
disabled: false
```
#### Which issue(s) this PR fixes:
Fixes#2827
#### Special notes for your reviewer:
1. Start Halo
2. Browse any page twice
3. See the difference in request times
#### Does this PR introduce a user-facing change?
```release-note
支持模板渲染结果缓存
```
#### What type of PR is this?
/kind feature
/area core
/area plugin
#### What this PR does / why we need it:
This PR adds property sources into PluginApplicationContext environment to support configuration properties mechanism.
See https://github.com/halo-dev/halo/issues/4015 for more.
#### Which issue(s) this PR fixes:
Fixes https://github.com/halo-dev/halo/issues/4015
#### Special notes for your reviewer:
You can verify the mechanism in [plugin-starter](https://github.com/halo-dev/plugin-starter) according to documentation `docs/developer-guide/plugin-configuration-properties.md`.
I've only tested it on macOS, looking forward to feedback on Windows.
#### Does this PR introduce a user-facing change?
```release-note
支持在插件中定义 @ConfigurationProperties 注解
```
#### What type of PR is this?
/kind feature
/area core
/milestone 2.0
#### What this PR does / why we need it:
This PR mainly implement full-text search of posts and provide extension point for other search engine.
Meanwhile, I implement ExtensionGetter to get implemention(s) of extension point from system ConfigMap.
But there still are something to do here:
- [x] Udpate documents when posts are published or posts are becoming unpublic.
- [x] Delete documents when posts are unpublished or deleted.
Because I'm waiting for https://github.com/halo-dev/halo/pull/2659 got merged.
I create two endpoints:
1. For full-text search of post
```bash
curl -X 'GET' \
'http://localhost:8090/apis/api.halo.run/v1alpha1/indices/post?keyword=halo&limit=10000&highlightPreTag=%3CB%3E&highlightPostTag=%3C%2FB%3E' \
-H 'accept: */*'
```
1. For refreshing indices
```bash
curl -X 'POST' \
'http://localhost:8090/apis/api.console.halo.run/v1alpha1/indices/post' \
-H 'accept: */*' \
-d ''
```
#### Which issue(s) this PR fixes:
Fixes #https://github.com/halo-dev/halo/issues/2637
#### Special notes for your reviewer:
#### Does this PR introduce a user-facing change?
```release-note
提供文章全文搜索功能并支持搜索引擎扩展
```
#### What type of PR is this?
/kind improvement
/kind api-change
/area core
/milestone 2.0
#### What this PR does / why we need it:
Please see b092b390b7/docs/authentication/README.md
#### Which issue(s) this PR fixes:
Fixes https://github.com/halo-dev/halo/issues/2506
#### Special notes for your reviewer:
#### Does this PR introduce a user-facing change?
```release-note
优化系统登录和登出逻辑
```
#### What type of PR is this?
/kind improvement
/kind api-change
/area core
/milestone 2.0
#### What this PR does / why we need it:
- 修改管理后台使用的自定义 API 的 group 为 `api.console.halo.run`
- 面向三方应用的自定义 API 的 group 为 `api.halo.run`
- 插件的自定义 API 的 group 为 `api.plugin.halo.run`
#### Which issue(s) this PR fixes:
Fixes#2418
#### Special notes for your reviewer:
/cc @halo-dev/sig-halo
#### Does this PR introduce a user-facing change?
```release-note
None
```
guqing