Get snapshot rest client cleanups (#31740)

This is a followup to #31537. It makes a number of changes requested by
a review that came after the PR was merged. These are mostly cleanups
and doc improvements.

client/rest-high-level/src/test/java/org/elasticsearch/client/RequestConvertersTests.java

@@ -2122,13 +2122,21 @@ public class RequestConvertersTests extends ESTestCase {
         getSnapshotsRequest.snapshots(Arrays.asList(snapshot1, snapshot2).toArray(new String[0]));
         setRandomMasterTimeout(getSnapshotsRequest, expectedParams);
 
-        boolean ignoreUnavailable = randomBoolean();
-        getSnapshotsRequest.ignoreUnavailable(ignoreUnavailable);
-        expectedParams.put("ignore_unavailable", Boolean.toString(ignoreUnavailable));
+        if (randomBoolean()) {
+            boolean ignoreUnavailable = randomBoolean();
+            getSnapshotsRequest.ignoreUnavailable(ignoreUnavailable);
+            expectedParams.put("ignore_unavailable", Boolean.toString(ignoreUnavailable));
+        } else {
+            expectedParams.put("ignore_unavailable", Boolean.FALSE.toString());
+        }
 
-        boolean verbose = randomBoolean();
-        getSnapshotsRequest.verbose(verbose);
-        expectedParams.put("verbose", Boolean.toString(verbose));
+        if (randomBoolean()) {
+            boolean verbose = randomBoolean();
+            getSnapshotsRequest.verbose(verbose);
+            expectedParams.put("verbose", Boolean.toString(verbose));
+        } else {
+            expectedParams.put("verbose", Boolean.TRUE.toString());
+        }
 
         Request request = RequestConverters.getSnapshots(getSnapshotsRequest);
         assertThat(endpoint, equalTo(request.getEndpoint()));

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/SnapshotClientDocumentationIT.java

@@ -48,7 +48,10 @@ import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.repositories.fs.FsRepository;
 import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.snapshots.SnapshotId;
 import org.elasticsearch.snapshots.SnapshotInfo;
+import org.elasticsearch.snapshots.SnapshotShardFailure;
+import org.elasticsearch.snapshots.SnapshotState;
 
 import java.io.IOException;
 import java.util.HashMap;
@@ -496,7 +499,14 @@ public class SnapshotClientDocumentationIT extends ESRestHighLevelClientTestCase
         // end::get-snapshots-execute
 
         // tag::get-snapshots-response
-        List<SnapshotInfo> snapshotsInfos = response.getSnapshots(); // <1>
+        List<SnapshotInfo> snapshotsInfos = response.getSnapshots();
+        SnapshotInfo snapshotInfo = snapshotsInfos.get(0);
+        RestStatus restStatus = snapshotInfo.status(); // <1>
+        SnapshotId snapshotId = snapshotInfo.snapshotId(); // <2>
+        SnapshotState snapshotState = snapshotInfo.state(); // <3>
+        List<SnapshotShardFailure> snapshotShardFailures = snapshotInfo.shardFailures(); // <4>
+        long startTime = snapshotInfo.startTime(); // <5>
+        long endTime = snapshotInfo.endTime(); // <6>
         // end::get-snapshots-response
         assertEquals(1, snapshotsInfos.size());
     }

docs/java-rest/high-level/snapshot/get_snapshots.asciidoc

@@ -93,11 +93,16 @@ argument.
 [[java-rest-high-snapshot-get-snapshots-response]]
 ==== Get Snapshots Response
 
-Use the `GetSnapshotsResponse` to retrieve information about the evaluated
-request:
+The returned `GetSnapshotsResponse` allows the retrieval of information about the requested
+snapshots:
 
 ["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
 include-tagged::{doc-tests}/SnapshotClientDocumentationIT.java[get-snapshots-response]
 --------------------------------------------------
-<1> Indicates the node has started the request.
+<1> The REST status of a snapshot
+<2> The snapshot id
+<3> The current state of the snapshot
+<4> Information about failures that occurred during the shard snapshot process.
+<5> The snapshot start time
+<6> The snapshot end time

server/src/main/java/org/elasticsearch/snapshots/SnapshotShardFailure.java

@@ -112,9 +112,9 @@ public class SnapshotShardFailure implements ShardOperationFailedException {
     }
 
     /**
-     * Returns REST status corresponding to this failure
+     * Returns {@link RestStatus} corresponding to this failure
      *
-     * @return REST STATUS
+     * @return REST status
      */
     @Override
     public RestStatus status() {