Plugins: Include license and notice files in zip (#23191)

This commit adds the elasticsearch LICENSE.txt to all plugins that
released with elasticsearch, as well as a generated NOTICE.txt specific
to the dependencies of each plugin.

buildSrc/src/main/groovy/org/elasticsearch/gradle/plugin/PluginBuildPlugin.groovy

@@ -19,6 +19,7 @@
 package org.elasticsearch.gradle.plugin
 
 import org.elasticsearch.gradle.BuildPlugin
+import org.elasticsearch.gradle.NoticeTask
 import org.elasticsearch.gradle.test.RestIntegTestTask
 import org.elasticsearch.gradle.test.RunTask
 import org.gradle.api.Project
@@ -71,6 +72,7 @@ public class PluginBuildPlugin extends BuildPlugin {
                 project.integTest.clusterConfig.plugin(project.path)
                 project.tasks.run.clusterConfig.plugin(project.path)
                 addZipPomGeneration(project)
+                addNoticeGeneration(project)
             }
 
             project.namingConventions {
@@ -244,4 +246,23 @@ public class PluginBuildPlugin extends BuildPlugin {
             }
         }
     }
+
+    protected void addNoticeGeneration(Project project) {
+        File licenseFile = project.pluginProperties.extension.licenseFile
+        if (licenseFile != null) {
+            project.bundlePlugin.into('/') {
+                from(licenseFile.parentFile) {
+                    include(licenseFile.name)
+                }
+            }
+        }
+        File noticeFile = project.pluginProperties.extension.licenseFile
+        if (noticeFile != null) {
+            NoticeTask generateNotice = project.tasks.create('generateNotice', NoticeTask.class)
+            generateNotice.dependencies(project)
+            project.bundlePlugin.into('/') {
+                from(generateNotice)
+            }
+        }
+    }
 }

buildSrc/src/main/groovy/org/elasticsearch/gradle/plugin/PluginPropertiesExtension.groovy

@@ -43,6 +43,17 @@ class PluginPropertiesExtension {
     @Input
     boolean hasClientJar = false
 
+    /** A license file that should be included in the built plugin zip. */
+    @Input
+    File licenseFile = null
+
+    /**
+     * A notice file that should be included in the built plugin zip. This will be
+     * extended with notices from the {@code licenses/} directory.
+     */
+    @Input
+    File noticeFile = null
+
     PluginPropertiesExtension(Project project) {
         name = project.name
         version = project.version

plugins/build.gradle

@@ -26,5 +26,8 @@ configure(subprojects.findAll { it.parent.path == project.path }) {
   esplugin {
     // for local ES plugins, the name of the plugin is the same as the directory
     name project.name
+    
+    licenseFile rootProject.file('LICENSE.txt')
+    noticeFile rootProject.file('NOTICE.txt')
   }
 }