refactor: use contains() for associative-container membership checks

src/iceberg/catalog/rest/auth/auth_properties.cc

@@ -62,7 +62,7 @@ Result<AuthProperties> AuthProperties::FromProperties(
   }
 
   // Resolve token endpoint: if not explicitly set, derive from catalog URI
-  if (properties.find(kOAuth2ServerUri.key()) == properties.end() ||
+  if (!properties.contains(kOAuth2ServerUri.key()) ||
       properties.at(kOAuth2ServerUri.key()).empty()) {
     auto uri_it = properties.find(RestCatalogProperties::kUri.key());
     if (uri_it != properties.end() && !uri_it->second.empty()) {

src/iceberg/metadata_columns.cc

@@ -58,12 +58,11 @@ const std::set<int32_t>& MetadataColumns::MetadataFieldIds() {
 }
 
 bool MetadataColumns::IsMetadataColumn(std::string_view name) {
-  return name == kPartitionColumnName ||
-         GetMetadataColumnMap().find(name) != GetMetadataColumnMap().end();
+  return name == kPartitionColumnName || GetMetadataColumnMap().contains(name);
 }
 
 bool MetadataColumns::IsMetadataColumn(int32_t id) {
-  return GetMetadataFieldIdSet().find(id) != GetMetadataFieldIdSet().end();
+  return GetMetadataFieldIdSet().contains(id);
 }
 
 Result<const SchemaField*> MetadataColumns::MetadataColumn(std::string_view name) {

src/iceberg/util/content_file_util.cc

@@ -98,7 +98,7 @@ template <typename V>
 void DropUnselectedColumnStats(std::map<int32_t, V>& map,
                                const std::unordered_set<int32_t>& columns) {
   for (auto it = map.begin(); it != map.end();) {
-    if (columns.find(it->first) == columns.end()) {
+    if (!columns.contains(it->first)) {
       it = map.erase(it);
     } else {
       ++it;

src/iceberg/util/struct_like_set.cc

@@ -580,7 +580,7 @@ Result<bool> StructLikeSet<kValidate>::Contains(const StructLike& row) const {
   if constexpr (kValidate) {
     ICEBERG_RETURN_UNEXPECTED(ValidateRowAgainstTypes(row, field_types_));
   }
-  return set_.find(row) != set_.end();
+  return set_.contains(row);
 }
 
 template <bool kValidate>