crowd2-plugin will no longer work once apache-httpcomponents-client-4-api is updated.

Steps to reproduce:

1. Package latest master of https://github.com/jenkinsci/apache-httpcomponents-client-4-api-plugin. You'll get `apache-httpcomponents-client-4-api.hpi`.

   docker run -it --rm -v "$(pwd):/workspace" -w /workspace maven:3.8.1-jdk-8 mvn package
   

1. Launch a new Jenkins instance (docker run --rm -it -p 8080:8080 jenkins/jenkins:lts-alpine) and complete the initial wizard. You don't need to install any plugin here. "Select plugin to install" and selecting "None" does that.
2. Install `apache-httpcomponents-client-4-api.hpi` in Manage Jenkins > Manage Plugins > Advanced > Deploy Plugin. Check "Restart Jenkins when installation is complete and no jobs are running"
3. Install jaxb plugin in Manage Jenkins > Manage Plugins > Available.
   • To see jaxb doesn't work even if it's installed, as crowd2 doesn't depend on that explicitly.
4. Install crowd2 plugin in Manage Jenkins > Manage Plugins > Available.
5. Go to Manage Jenkins > Configure Global Security. Run "Check Connection" with Crowd 2 in Security Realm. You don't need an actual crowd2 server and can use following dummy configurations as we just verify the connection behavior here:
   • • Crowd URL: http://localhost:8888/
     • Application Name: Jenkins
     • Application Password: Jenkins
6. The check fails with "ERROR". It should fail with "The connection check failed." if crowd2 works properly.

Following stack trace is recorded in the system log:

2022-05-05 04:33:30.117+0000 [id=85]    WARNING o.e.j.s.h.ContextHandler$Context#log: Error while serving http://localhost:8080/descriptorByName/de.theit.jenkins.crowd.CrowdSecurityRealm/testConnection
java.lang.ClassNotFoundException: javax.xml.bind.JAXBException
        at org.apache.tools.ant.AntClassLoader.findClassInComponents(AntClassLoader.java:1402)
        at org.apache.tools.ant.AntClassLoader.findClass(AntClassLoader.java:1357)
        at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:1112)
        at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
Caused: java.lang.NoClassDefFoundError: javax/xml/bind/JAXBException
        at com.atlassian.crowd.integration.rest.service.RestCrowdClient.<init>(RestCrowdClient.java:92)
        at com.atlassian.crowd.integration.rest.service.factory.RestCrowdClientFactory.newInstance(RestCrowdClientFactory.java:26)
...

Why this happens?:

• apache-httpcomponents-client-4-api depends on jaxb as "Implied dependency". That's because apache-httpcomponents-client-4-api-4.5.13-1.0 targets Jenkins-2.60.3. Jenkins <= 2.163 contained jaxb in it, and Jenkins > 2.163 automatically injects jaxb to dependencies of any plugins targeting Jenkins <= 2.163.
  • https://github.com/jenkinsci/jenkins/blob/jenkins-2.346/core/src/main/resources/jenkins/split-plugins.txt#L30
• So crowd2 can access jaxb via apache-httpcomponents-client-4-api-4.5.13-1.0.
• apache-httpcomponents-client-4-api itself doesn't need jaxb, and it's supposed to no longer depends on jaxb once it target jenkins > 2.163. Crowd2 will be not able to access jaxb.

Resolution:

• Add dependency to jaxb explicitly in crowd2. Just instructed in https://plugins.jenkins.io/jaxb/.