fix(replication): propagate metadata changes (#5635)

Preserve metadata replication operations in the durable MRF and route tagging, retention, and legal-hold updates through the existing full-object replication transport. Keep ACL propagation outside the contract because the current object model has no durable object ACL state.

Refs #1616

crates/replication/src/filemeta.rs

@@ -550,6 +550,8 @@ pub enum MrfOpKind {
     #[default]
     #[serde(rename = "object")]
     Object,
+    #[serde(rename = "metadata")]
+    Metadata,
     #[serde(rename = "delete")]
     Delete,
 }
@@ -831,7 +833,11 @@ impl ReplicationWorkerOperation for ReplicateObjectInfo {
             version_id: self.version_id,
             retry_count: retry_count_to_mrf(self.retry_count),
             size: self.size,
-            op: MrfOpKind::Object,
+            op: if self.op_type == ReplicationType::Metadata {
+                MrfOpKind::Metadata
+            } else {
+                MrfOpKind::Object
+            },
             delete_marker_version_id: None,
             delete_marker: false,
             delete_marker_mtime: None,
@@ -886,7 +892,11 @@ impl ReplicateObjectInfo {
             version_id: self.version_id,
             retry_count: retry_count_to_mrf(self.retry_count),
             size: self.size,
-            op: MrfOpKind::Object,
+            op: if self.op_type == ReplicationType::Metadata {
+                MrfOpKind::Metadata
+            } else {
+                MrfOpKind::Object
+            },
             delete_marker_version_id: None,
             delete_marker: false,
             delete_marker_mtime: None,
@@ -1114,6 +1124,18 @@ mod tests {
         assert_eq!(asynchronous.replicate_target_arns(), vec!["arn:async".to_string()]);
     }
 
+    #[test]
+    fn metadata_replication_mrf_entry_preserves_operation_kind() {
+        let info = ReplicateObjectInfo {
+            bucket: "bucket".to_string(),
+            name: "object".to_string(),
+            op_type: ReplicationType::Metadata,
+            ..Default::default()
+        };
+
+        assert_eq!(info.to_mrf_entry().op, MrfOpKind::Metadata);
+    }
+
     #[test]
     fn target_state_reads_resync_timestamp_from_target_reset_header_key() {
         let arn = "arn:rustfs:replication:us-east-1:target:bucket";