[Backport 2.x] Add default implementation to new finalizeSnapshot() i…

…n Repository (#16141)

* Add default implementation to new finalizeSnapshot() in Repository (#16128)

Signed-off-by: Sachin Kale <sachinpkale@gmail.com>
(cherry picked from commit 9a5c7b2)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

* Fix japicmp configuration by treating abstract-to-default method changes as non-breaking

Signed-off-by: Andriy Redko <andriy.redko@aiven.io>

---------

Signed-off-by: Sachin Kale <sachinpkale@gmail.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Signed-off-by: Andriy Redko <andriy.redko@aiven.io>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Andriy Redko <andriy.redko@aiven.io>

server/build.gradle

@@ -443,6 +443,8 @@ tasks.named("sourcesJar").configure {
 /** Compares the current build against a laltest released version or the version supplied through 'japicmp.compare.version' system property */
 tasks.register("japicmp", me.champeau.gradle.japicmp.JapicmpTask) {
     logger.info("Comparing public APIs from ${version} to ${japicmpCompareTarget}")
+    // See please https://github.com/siom79/japicmp/issues/201
+    compatibilityChangeExcludes = [ "METHOD_ABSTRACT_NOW_DEFAULT" ]
     oldClasspath.from(files("${buildDir}/japicmp-target/opensearch-${japicmpCompareTarget}.jar"))
     newClasspath.from(tasks.named('jar'))
     onlyModified = true

server/src/main/java/org/opensearch/repositories/Repository.java

@@ -193,7 +193,7 @@ void finalizeSnapshot(
      * @param repositoryUpdatePriority  priority for the cluster state update task
      * @param listener              listener to be invoked with the new {@link RepositoryData} after completing the snapshot
      */
-    void finalizeSnapshot(
+    default void finalizeSnapshot(
         ShardGenerations shardGenerations,
         long repositoryStateId,
         Metadata clusterMetadata,
@@ -202,7 +202,9 @@ void finalizeSnapshot(
         Function<ClusterState, ClusterState> stateTransformer,
         Priority repositoryUpdatePriority,
         ActionListener<RepositoryData> listener
-    );
+    ) {
+        throw new UnsupportedOperationException();
+    }
 
     /**
      * Deletes snapshots