Remove support for settings in restore requests (#53284)

The unused `settings` value was deprecated in #53268 so this commit removes it.

docs/reference/migration/migrate_8_0/snapshots.asciidoc

@@ -94,3 +94,10 @@ breaking change was made necessary by
 https://aws.amazon.com/blogs/aws/amazon-s3-path-deprecation-plan-the-rest-of-the-story/[AWS's
 announcement] that the path-style access pattern is deprecated and will be
 unsupported on buckets created after September 30th 2020.
+
+[float]
+==== Restore requests no longer accept settings
+
+In earlier versions, you could pass both `settings` and `index_settings` in the
+body of a restore snapshot request, but the `settings` value was ignored. The
+restore snapshot API now rejects requests that include a `settings` value.

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/restore/RestoreSnapshotRequest.java

@@ -19,7 +19,6 @@
 
 package org.elasticsearch.action.admin.cluster.snapshots.restore;
 
-import org.apache.logging.log4j.LogManager;
 import org.elasticsearch.ElasticsearchGenerationException;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.ActionRequestValidationException;
@@ -28,7 +27,6 @@ import org.elasticsearch.action.support.master.MasterNodeRequest;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
-import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.ToXContentObject;
 import org.elasticsearch.common.xcontent.XContentBuilder;
@@ -43,9 +41,9 @@ import java.util.Map;
 import java.util.Objects;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
+import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.xcontent.support.XContentMapValues.nodeBooleanValue;
 
 /**
@@ -53,8 +51,6 @@ import static org.elasticsearch.common.xcontent.support.XContentMapValues.nodeBo
  */
 public class RestoreSnapshotRequest extends MasterNodeRequest<RestoreSnapshotRequest> implements ToXContentObject {
 
-    private static final DeprecationLogger DEPRECATION_LOGGER = new DeprecationLogger(LogManager.getLogger(RestoreSnapshotRequest.class));
-
     private String snapshot;
     private String repository;
     private String[] indices = Strings.EMPTY_ARRAY;
@@ -459,12 +455,6 @@ public class RestoreSnapshotRequest extends MasterNodeRequest<RestoreSnapshotReq
                 }
             } else if (name.equals("partial")) {
                 partial(nodeBooleanValue(entry.getValue(), "partial"));
-            } else if (name.equals("settings")) {
-                if (!(entry.getValue() instanceof Map)) {
-                    throw new IllegalArgumentException("malformed settings section");
-                }
-                DEPRECATION_LOGGER.deprecatedAndMaybeLog("RestoreSnapshotRequest#settings",
-                    "specifying [settings] when restoring a snapshot has no effect and will not be supported in a future version");
             } else if (name.equals("include_global_state")) {
                 includeGlobalState = nodeBooleanValue(entry.getValue(), "include_global_state");
             } else if (name.equals("include_aliases")) {

server/src/test/java/org/elasticsearch/snapshots/SnapshotRequestsTests.java

@@ -66,7 +66,6 @@ public class SnapshotRequestsTests extends ESTestCase {
         builder.field("rename_replacement", "rename-to");
         boolean partial = randomBoolean();
         builder.field("partial", partial);
-        builder.startObject("settings").field("set1", "val1").endObject();
         builder.startObject("index_settings").field("set1", "val2").endObject();
         if (randomBoolean()) {
             builder.field("ignore_index_settings", "set2,set3");
@@ -96,8 +95,6 @@ public class SnapshotRequestsTests extends ESTestCase {
             ? indicesOptions.ignoreUnavailable()
             : IndicesOptions.strictExpandOpen().ignoreUnavailable();
         assertEquals(expectedIgnoreAvailable, request.indicesOptions().ignoreUnavailable());
-
-        assertWarnings("specifying [settings] when restoring a snapshot has no effect and will not be supported in a future version");
     }
 
     public void testCreateSnapshotRequestParsing() throws IOException {