fix: move Set to SnapshotUpdate

Author: zhjwpku

src/iceberg/update/fast_append.cc

@@ -93,11 +93,6 @@ FastAppend& FastAppend::ToBranch(const std::string& branch) {
   return *this;
 }
 
-FastAppend& FastAppend::Set(const std::string& property, const std::string& value) {
-  summary_.Set(property, value);
-  return *this;
-}
-
 std::string FastAppend::operation() { return DataOperation::kAppend; }
 
 Result<std::vector<ManifestFile>> FastAppend::Apply(

src/iceberg/update/fast_append.h

@@ -75,13 +75,6 @@ class ICEBERG_EXPORT FastAppend : public SnapshotUpdate {
   /// \return Reference to this for method chaining
   FastAppend& ToBranch(const std::string& branch);
 
-  /// \brief Set a summary property.
-  ///
-  /// \param property The property name
-  /// \param value The property value
-  /// \return Reference to this for method chaining
-  FastAppend& Set(const std::string& property, const std::string& value);
-
   std::string operation() override;
 
   Result<std::vector<ManifestFile>> Apply(
@@ -110,7 +103,6 @@ class ICEBERG_EXPORT FastAppend : public SnapshotUpdate {
 
  private:
   std::string table_name_;
-  SnapshotSummaryBuilder summary_;
   std::unordered_map<int32_t, DataFileSet> new_data_files_by_spec_;
   std::vector<ManifestFile> append_manifests_;
   std::vector<ManifestFile> rewritten_append_manifests_;

src/iceberg/update/snapshot_update.h

@@ -76,6 +76,16 @@ class ICEBERG_EXPORT SnapshotUpdate : public PendingUpdate {
     return self;
   }
 
+  /// \brief Set a summary property.
+  ///
+  /// \param property The property name
+  /// \param value The property value
+  /// \return Reference to this for method chaining
+  auto& Set(this auto& self, const std::string& property, const std::string& value) {
+    self.summary_.Set(property, value);
+    return self;
+  }
+
   /// \brief Apply the update's changes to create a new snapshot.
   ///
   /// This method validates the changes, applies them to the metadata,
@@ -179,6 +189,10 @@ class ICEBERG_EXPORT SnapshotUpdate : public PendingUpdate {
 
   std::string ManifestPath();
 
+ protected:
+  /// \brief Builder for tracking snapshot summary properties and metrics.
+  SnapshotSummaryBuilder summary_;
+
  private:
   /// \brief Returns the snapshot summary from the implementation and updates totals.
   Result<std::unordered_map<std::string, std::string>> ComputeSummary(