add missing formatter for Snowflake

src/discord/snowflake.hpp

@@ -2,6 +2,7 @@
 #include <cstdint>
 #include <nlohmann/json.hpp>
 #include <glibmm/ustring.h>
+#include <fmt/core.h>
 
 struct Snowflake {
     Snowflake();
@@ -39,6 +40,13 @@ private:
     unsigned long long m_num;
 };
 
+template<>
+struct fmt::formatter<Snowflake> : fmt::formatter<std::string> {
+    auto format(Snowflake id, format_context &ctx) -> decltype(ctx.out()) {
+        return format_to(ctx.out(), "[id: {}]", static_cast<uint64_t>(id));
+    }
+};
+
 namespace std {
 template<>
 struct hash<Snowflake> {