Improve the httpclient reg-tests to test the streaming,
The regtest now sends a big payload to vtest, then receive a payload
from vtest and send it again.
Add support for HEAD/PUT/POST/DELETE method with the lua httpclient.
This patch use the httpclient_req_gen() function with a different meth
parameter to implement this.
Also change the reg-test to support a POST request with a body.
httpclient_req_gen() takes a payload argument which can be use to put a
payload in the request. This payload can only fit a request buffer.
This payload can also be specified by the "body" named parameter within
the lua. httpclient.
It is also used within the CLI httpclient when specified as a CLI
payload with "<<".
Migrate the httpclient:get() method to named arguments so we can
specify optional arguments.
This allows to pass headers as an optional argument as an array.
The () in the method call must be replaced by {}:
local res = httpclient:get{url="http://127.0.0.1:9000/?s=99",
headers= {["X-foo"] = { "salt" }, ["X-bar"] = {"pepper" }}}
This reg-test is heavily inspired by the lua_socket.vtc one.
It replaces the HTTP/1.1 request made manually with a socket object with
an httpclient object.
