actually pass file type to image::write()

src/main.cpp

@@ -95,7 +95,7 @@ int main(int /*argc*/, char * /*argv*/[]) {
             }
         }
 
-        image::write(img);
+        image::write(img, req.magick);
 
     } catch (const std::runtime_error &e) {
         if (std::strlen(e.what()) != 0) {

src/types.hpp

@@ -18,6 +18,7 @@
 #define LIBRAVATARSERV_TYPES_HPP
 
 #include <cstdint>
+#include <optional>
 #include <string>
 namespace libravatarserv {
 
@@ -31,7 +32,7 @@ struct request_t {
     algorithm_t algo;
     std::int16_t size;
     std::string fallback;
-    std::string magick;
+    std::optional<std::string> magick;
 };
 
 } // namespace libravatarserv