[skip ci] Several documentation related FIXME resolved.

dev/restinio/sendfile.hpp

@@ -529,8 +529,18 @@ sendfile(
 			chunk_size );
 }
 
-//FIXME: document this!
 /*!
+ * @brief Creates an instance for service sendfile operation.
+ *
+ * This overload accepts `std::filesystem::path` as file name.
+ *
+ * @note
+ * On Windows it uses `std::filesystem::path::wstring()` for opening
+ * the file. It means that on Windows UNICODE-based version of
+ * file-related functions are used and file names with UNICODE symbols
+ * are supported. On UNIX platforms `std::filesystem::path::string()` is
+ * used and it's assumed that file names are in UTF-8.
+ *
  * @since v.0.7.1
  */
 [[nodiscard]]

dev/restinio/sendfile_defs_default.hpp

@@ -41,8 +41,15 @@ using file_size_t = std::uint64_t;
 [[nodiscard]]
 constexpr file_descriptor_t null_file_descriptor(){ return nullptr; }
 
-//FIXME: document platform-specific behavior.
 //! Open file.
+/*!
+ * @note
+ * It uses `fopen_s` if the compiler is VC++.
+ *
+ * @note
+ * It's expected that @a file_path contains names in ANSI encoding
+ * on Windows platform.
+ */
 [[nodiscard]]
 inline file_descriptor_t
 open_file( const char * file_path )
@@ -79,10 +86,16 @@ open_file( const char * file_path )
 #endif
 }
 
-//FIXME: document platform-specific behavior!
 /*!
  * @brief Helper function that accepts std::filesystem::path.
  *
+ * @note
+ * It uses `_wfopen_s` if the compiler is VC++.
+ *
+ * @note
+ * It's expected that @a file_path contains names in ANSI encoding
+ * on Windows platform.
+ *
  * @since v.0.7.1
  */
 [[nodiscard]]