added alert suport

Author: mateusmoutinho

src/session/extra.lua

@@ -2,11 +2,15 @@ PublicSession.get_session_id = function(public, private)
     return private.session_id
 end
 
-PublicSession.accept_alert = function(public, private)
+PublicSession.accept_alert = function(_, private)
     local result = private.fetch({
         url = private.url .. "/session/" .. private.session_id .. "/alert/accept",
         method = "POST",
-        http_version = "1.1"
+        http_version = "1.1",
+        headers = {
+            ["Content-Type"] = "application/json"
+        },
+        body = {}
     })
 
     if result.status_code ~= 200 then