Allow update sites to define a custom URL for wizard plugin suggestion (

#8951)

* currently suggested plugins list as setup time is hardcoded, we can make it configurable

Signed-off-by: Olivier Lamy <olamy@apache.org>

* add new method to UpdateSite to avoid using System property

Signed-off-by: Olivier Lamy <olamy@apache.org>

* Update core/src/main/java/hudson/model/UpdateSite.java

Co-authored-by: Tim Jacomb <21194782+timja@users.noreply.github.com>

---------

Signed-off-by: Olivier Lamy <olamy@apache.org>
Co-authored-by: Tim Jacomb <21194782+timja@users.noreply.github.com>
Co-authored-by: Alexander Brandes <mc.cache@web.de>

core/src/main/java/hudson/model/UpdateSite.java

@@ -493,6 +493,17 @@ public String getUrl() {
         return url;
     }
 
+    /**
+     *
+     * @return the URL used by {@link jenkins.install.SetupWizard} for suggested plugins to install at setup time
+     * @since TODO
+     */
+    @Exported
+    public String getSuggestedPluginsUrl() {
+        String updateCenterJsonUrl = getUrl();
+        return updateCenterJsonUrl.replace("/update-center.json", "/platform-plugins.json");
+    }
+
 
     /**
      * URL which exposes the metadata location in a specific update site.

core/src/main/java/jenkins/install/SetupWizard.java

@@ -553,8 +553,7 @@ public JSONArray getPlatformPluginUpdates() {
         Jenkins.get().checkPermission(Jenkins.ADMINISTER);
         JSONArray initialPluginList = null;
         updateSiteList: for (UpdateSite updateSite : Jenkins.get().getUpdateCenter().getSiteList()) {
-            String updateCenterJsonUrl = updateSite.getUrl();
-            String suggestedPluginUrl = updateCenterJsonUrl.replace("/update-center.json", "/platform-plugins.json");
+            String suggestedPluginUrl = updateSite.getSuggestedPluginsUrl();
             VersionNumber version = Jenkins.getVersion();
             if (version != null && (suggestedPluginUrl.startsWith("https://") || suggestedPluginUrl.startsWith("http://"))) {
                 // Allow remote update site to distinguish based on the current version