#### What type of PR is this?
/kind feature
/area core
/area plugin
#### What this PR does / why we need it:
This PR enhance usage of SharedEvent annotation to add support for publishing events among plugins.
#### How to test?
1. Clone repository https://github.com/halo-dev/plugin-starter
2. Change build.gradle as following:
```gradle
dependencies {
implementation platform('run.halo.tools.platform:plugin:2.17.0-SNAPSHOT')
```
3. Change StarterPlugin as following:
```java
@Component
public class StarterPlugin extends BasePlugin {
private final ApplicationContext appContext;
public StarterPlugin(PluginContext pluginContext, ApplicationContext appContext) {
super(pluginContext);
this.appContext = appContext;
}
@Override
public void start() {
appContext.publishEvent(new PostDeletedEvent(this, "fake-plugin"));
}
@Override
public void stop() {
}
@EventListener(PostDeletedEvent.class)
public void onApplicationEvent(PostDeletedEvent event) {
System.out.println("Post deleted event received in plugin: " + event.getName());
}
}
```
4. Add a listener to Halo core
```java
@EventListener(PostDeletedEvent.class)
public void onApplicationEvent(PostDeletedEvent event) {
System.out.println("Post deleted event received in core: " + event.getName());
}
```
5. Build plugin and install plugin
6. Enable the plugin and see the result
#### Does this PR introduce a user-facing change?
```release-note
None
```
#### What type of PR is this?
/kind feature
/area core
/area plugin
#### What this PR does / why we need it:
This PR allows plugin developers defining WebSocket endpoints in plugins.
#### Which issue(s) this PR fixes:
Fixes#5285
#### Does this PR introduce a user-facing change?
```release-note
支持在插件中实现 WebSocket
```
John Niang