Document that Crowd2 plugin distribution will be suspended (#240)

* Document that plugin distribution will be suspended

The Crowd 2 integration plugin is using dependencies that are closed
source and are not licensed with an OSI approved open source license.

The Jenkins project governance document and the plugin hosting page
state that we only deliver plugins with open source licenses.

The specific license of concern is:

* https://www.atlassian.com/legal/software-license-agreement
  Atlassian customer license

The same license of concern is used for:

* http://www.atlassian.com/end-user-agreement/
  Atlassian 3.0 End User License Agreement

From the `/plugin/crowd2/wrapper/thirdPartyLicenses` page of a Jenkins
installation that includes the Crowd 2 plugin:

Dependencies using the Atlassian Customer Agreement:

* com.atlassian.crowd:crowd-integration-api:5.1.5
* com.atlassian.crowd:crowd-integration-client-rest:5.1.5
* com.atlassian.crowd:embedded-crowd-api:5.1.5
* com.atlassian.crowd:crowd-integration-client-common:5.1.5

Dependencies using the Atlassian 3.0 End User License Agreement

* com.atlassian.collectors:atlassian-collectors-util:1.1

* Link to Crowd Server end of life announcement

https://www.atlassian.com/licensing/crowd#crowd-data-center says:

Important changes to our Server and Data Center products

We’ve ended sales for new server licenses and will end support for
server on February 15, 2024 PT. We’re continuing investment in Data
Center with several key improvements.

https://www.atlassian.com/migration/assess/journey-to-cloud provides a
migration path.

README.md

@@ -1,3 +1,18 @@
+# [Plugin distribution suspended](https://github.com/jenkins-infra/helpdesk/issues/3854)
+
+Distribution of this plugin has been suspended by the Jenkins project because it uses several closed source dependencies.
+The closed source dependencies in the most recent release include:
+
+* com.atlassian.crowd:crowd-integration-api:5.1.5
+* com.atlassian.crowd:crowd-integration-client-rest:5.1.5
+* com.atlassian.crowd:embedded-crowd-api:5.1.5
+* com.atlassian.crowd:crowd-integration-client-common:5.1.5
+* com.atlassian.collectors:atlassian-collectors-util:1.1
+
+The Jenkins project [governance document](https://www.jenkins.io/project/governance/#license) and the [plugin hosting instructions](https://www.jenkins.io/doc/developer/publishing/preparation/#license) both note that the Jenkins project requires that plugins distributed by the Jenkins project must be open source and use open source dependencies.
+
+Atlassian has announced [Crowd Server will no longer be supported after February 15, 2024](https://www.atlassian.com/licensing/crowd#crowd-data-center).
+Users of Crowd Server must migrate to Crowd Data Center.
 
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