add headers to evpp implementation

src/utils/EvppRequest.cpp

@@ -91,6 +91,15 @@ void EvppRequest::ExecuteInLoop() {
         goto failed;
     }
 
+    /**
+     * add custom headers
+     */
+    if (!headers_map_.empty()){
+        for (auto entry : headers_map_){
+           evhttp_add_header(req->output_headers, entry.first.c_str(), entry.second.c_str()); 
+        }
+    }
+
     if (!body_.empty()) {
         //req_type = EVHTTP_REQ_POST;
         if (evbuffer_add(req->output_buffer, body_.c_str(), body_.size())) {

src/utils/EvppRequest.h

@@ -56,6 +56,13 @@ public:
     void set_retry_interval(Duration d) {
         retry_interval_ = d;
     }
+    void add_header(const std::string& header, const std::string& value){
+        headers_map_[header] = value;
+    }
+    void add_headers(std::map<std::string,std::string>& headers_map){
+        headers_map_.insert(headers_map.begin(), headers_map.end());
+    }
+
 private:
     static void HandleResponse(struct evhttp_request* r, void* v);
     void HandleResponse(struct evhttp_request* r);
@@ -72,6 +79,7 @@ private:
     std::shared_ptr<Conn> conn_;
     EvppHandler handler_;
     evhttp_cmd_type req_type_;
+    std::map<std::string,std::string> headers_map_;
 
     // The retried times
     int retried_ = 0;
@@ -88,6 +96,9 @@ typedef std::shared_ptr<EvppRequest> EvppRequestPtr;
 
 class GetEvppRequest : public EvppRequest {
 public:
+    GetEvppRequest(EventLoop* loop, const std::string& url, const std::string& body, Duration timeout)
+        : EvppRequest(loop, EVHTTP_REQ_GET,url, body, timeout) {}
+
     GetEvppRequest(ConnPool* pool, EventLoop* loop, const std::string& uri_with_param)
         : EvppRequest(pool, loop, EVHTTP_REQ_GET, uri_with_param, empty_) {}