Add add-metadata-hints goal to Maven Plugin

Update the maven plugin with a new `add-metadata-hints` goal that can
be used to bundle hints obtained from the metadata repository into
the jar.

Author: philwebb

docs/src/docs/asciidoc/maven-plugin.adoc

@@ -660,6 +660,23 @@ This may be interesting if there's no specific metadata available for the partic
 include::../../../../samples/native-config-integration/pom.xml[tag=metadata-force-version]
 ----
 
+=== Adding metadata respoistory files
+
+By default, repository metadata will be used only when your native image is generated.
+In some situations, you may want to include the metadata directly inside your jar.
+
+Adding metadata to your jar can be useful when some other process is responsible for converting your jar into a native image.
+For example, you might be generating a shaded jar and using a https://paketo.io/[Paketo buildpack] to convert it to a native image.
+
+To include metadata repository inside your jar you can use the `add-metadata-hints` goal.
+Typically the goal will be included an execution step where by default it will be bound to the `generate-resources` phase:
+
+.Configuring the `add-metadata-hints` goal to execute with the `generate-resources` phase
+[source,xml,indent=0]
+----
+include::../../../../samples/native-config-integration/pom.xml[tag=add-metadata-hints-execution]
+----
+
 [[javadocs]]
 == Javadocs
 

native-maven-plugin/src/functionalTest/groovy/org/graalvm/buildtools/maven/MetadataRepositoryFunctionalTest.groovy

@@ -175,4 +175,23 @@ class MetadataRepositoryFunctionalTest extends AbstractGraalVMMavenFunctionalTes
         outputContains "Failed to download from https://httpstat.us/404: 404 Not Found"
     }
 
+    void "it can include hints in jar"() {
+        given:
+        withSample("native-config-integration")
+
+        when:
+        mvn '-X', '-PaddMetadataHints', '-DskipTests', 'package'
+
+        then:
+        buildSucceeded
+
+        and:
+        file("target/classes/META-INF/native-image/org.graalvm.internal/library-with-reflection/1.5/reflect-config.json").text.trim() == '''[
+  {
+    "name": "org.graalvm.internal.reflect.Message",
+    "allDeclaredFields": true,
+    "allDeclaredMethods": true
+  }
+]'''
+    }
 }