rgw: add missing last_modified field to swift api

Fixes: https://tracker.ceph.com/issues/68195
Signed-off-by: Andrei Ivashchenko <[email protected]>

Author: aiivashchenko

src/rgw/rgw_common.h

@@ -1426,6 +1426,7 @@ struct RGWBucketEnt {
   size_t size;
   size_t size_rounded;
   ceph::real_time creation_time;
+  ceph::real_time modification_time;
   uint64_t count;
 
   /* The placement_rule is necessary to calculate per-storage-policy statics

src/rgw/rgw_rest_swift.cc

@@ -361,6 +361,7 @@ void RGWListBuckets_ObjStore_SWIFT::dump_bucket_entry(const RGWBucketEnt& ent)
   if (need_stats) {
     s->formatter->dump_int("count", ent.count);
     s->formatter->dump_int("bytes", ent.size);
+    dump_time(s, "last_modified", ent.modification_time);
   }
 
   s->formatter->close_section();

src/rgw/services/svc_bucket_sobj.cc

@@ -556,7 +556,7 @@ int RGWSI_Bucket_SObj::read_bucket_stats(const rgw_bucket& bucket,
                                          const DoutPrefixProvider *dpp)
 {
   RGWBucketInfo bucket_info;
-  int ret = read_bucket_info(bucket, &bucket_info, nullptr, nullptr, boost::none, y, dpp);
+  int ret = read_bucket_info(bucket, &bucket_info, &ent->modification_time, nullptr, boost::none, y, dpp);
   if (ret < 0) {
     return ret;
   }