remove cpr as a dependency (#21)

abstract away library usage

discord/httpclient.hpp

@@ -0,0 +1,37 @@
+#pragma once
+#include <functional>
+#include <future>
+#include <string>
+#include <unordered_map>
+#include <memory>
+#include <mutex>
+#include <queue>
+#include <glibmm.h>
+#include "../http.hpp"
+
+class HTTPClient {
+public:
+    HTTPClient(std::string api_base);
+
+    void SetUserAgent(std::string agent);
+    void SetAuth(std::string auth);
+    void MakeDELETE(const std::string &path, std::function<void(http::response_type r)> cb);
+    void MakeGET(const std::string &path, std::function<void(http::response_type r)> cb);
+    void MakePATCH(const std::string &path, const std::string &payload, std::function<void(http::response_type r)> cb);
+    void MakePOST(const std::string &path, const std::string &payload, std::function<void(http::response_type r)> cb);
+    void MakePUT(const std::string &path, const std::string &payload, std::function<void(http::response_type r)> cb);
+
+private:
+    void OnResponse(const http::response_type &r, std::function<void(http::response_type r)> cb);
+    void CleanupFutures();
+
+    mutable std::mutex m_mutex;
+    Glib::Dispatcher m_dispatcher;
+    std::queue<std::function<void()>> m_queue;
+    void RunCallbacks();
+
+    std::vector<std::future<void>> m_futures;
+    std::string m_api_base;
+    std::string m_authorization;
+    std::string m_agent;
+};