### What changes were proposed in this pull request?
We used `jersey2` library for celeborn-openapi-client before, and I found that there is dependencies lack issue for shaded celeborn-openapi-client.
I tried to raise a [PR #2640] to fix it, but seems It is difficult to maintain the dependencies transition from jersey dependencies.
And I received the suggestion from pan to migrate the library from jersey2 to `apache-httpclient`.
FYI: for https://openapi-generator.tech/docs/generators/java/
<img width="500" alt="image" src="https://github.com/user-attachments/assets/d102a7c9-46cd-4fd7-a2a0-7396a815776d">
To leverage the latest openapi-generator plugin, I upgrade the openapi-generator version to latest 7.7.0 and it requires JDK11+.
Due celeborn does not drop the Java8 support so far, so I include the generated code into repo and add user guide for re-generation.
### Why are the changes needed?
To fix dependencies leak issue and maintain the dependencies easily.
### Does this PR introduce _any_ user-facing change?
No, this SDK has not been released, so no user-facing change.
### How was this patch tested?
Testing with sample maven project.
pom.xml:
```
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>test_openapi</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.apache.celeborn</groupId>
<artifactId>celeborn-openapi-client_2.12</artifactId>
<version>0.6.0-SNAPSHOT</version>
</dependency>
</dependencies>
</project>
```
Testing code:
```
package org.example;
import org.apache.celeborn.rest.v1.master.MasterApi;
import org.apache.celeborn.rest.v1.master.WorkerApi;
import org.apache.celeborn.rest.v1.master.invoker.ApiClient;
public class Main {
public static void main(String[] args) throws Exception {
String cmUrl = "http://***:9098";
MasterApi masterApi = new MasterApi(new ApiClient().setBasePath(cmUrl));
System.out.println(masterApi.getMasterGroupInfo().getLeader().getAddress().split(":")[0]);
WorkerApi workerApi = new WorkerApi(new ApiClient().setBasePath(cmUrl));
System.out.println(workerApi.getWorkers());
System.out.println(workerApi.getWorkerEvents());
}
}
```
```
java -Dfile.encoding=UTF-8 -classpath /Users/fwang12/todo/test_openapi/target/classes:/Users/fwang12/todo/celeborn/openapi/openapi-client/target/celeborn-openapi-client_2.12-0.6.0-SNAPSHOT.jar org.example.Main
```
<img width="1727" alt="image" src="https://github.com/user-attachments/assets/2da8b126-be96-4c37-9a33-ba196024f2ba">
Closes#2641 from turboFei/appache_httpclient.
Lead-authored-by: Wang, Fei <fwang12@ebay.com>
Co-authored-by: Fei Wang <cn.feiwang@gmail.com>
Co-authored-by: Cheng Pan <pan3793@gmail.com>
Signed-off-by: Shuang <lvshuang.xjs@alibaba-inc.com>
1515ed38b2