Added 2 functions (column_size and column_mod) under pqxx::result file (

#727)

Support `PQfsize()` and `PQfmod()`.

include/pqxx/result.hxx

@@ -194,6 +194,20 @@ public:
   /// Name of column with this number (throws exception if it doesn't exist)
   [[nodiscard]] char const *column_name(row_size_type number) const &;
 
+  /// Size in bytes of column with this number
+  /** This is the size of the server's internal representation of the data type.
+   * A negative value indicates the data type is variable-length.
+   */
+  /// This is the size of the server's internal representation of the data type
+  [[nodiscard]] int column_storage(row_size_type number) const noexcept;
+
+  /// Type modifier of the column with this number
+  /** The interpretation of modifier values is type-specific; they typically indicate precision or size limits.
+   * The value -1 is used to indicate “no information available”.
+   * Most data types do not use modifiers, in which case the value is always -1.
+   */
+  [[nodiscard]] int column_type_modifier(row_size_type number) const noexcept;
+
   /// Return column's type, as an OID from the system catalogue.
   [[nodiscard]] oid column_type(row_size_type col_num) const;
 

src/result.cxx

@@ -502,6 +502,18 @@ pqxx::row::size_type pqxx::result::columns() const noexcept
 }
 
 
+int pqxx::result::column_storage(pqxx::row::size_type number) const noexcept
+{
+  return PQfsize(m_data.get(), number);
+}
+
+
+int pqxx::result::column_type_modifier(pqxx::row::size_type number) const noexcept
+{
+  return PQfmod(m_data.get(), number);
+}
+
+
 // const_result_iterator
 
 pqxx::const_result_iterator pqxx::const_result_iterator::operator++(int)