tests: add httpcommon tests and add new file_handler methods (#2712)

Co-authored-by: Mariotaku <mariotaku.lee@gmail.com>

src/file_handler.h

@@ -7,8 +7,15 @@
 #include <string>
 
 namespace file_handler {
+  std::string
+  get_parent_directory(const std::string &path);
+
+  bool
+  make_directory(const std::string &path);
+
   std::string
   read_file(const char *path);
+
   int
   write_file(const char *path, const std::string_view &contents);
 }  // namespace file_handler