http_async_client: add curl_follow_redirect parameter

- add curl_follow_redirect mod parameter to set CURLOPT_FOLLOWLOCATION
  to tell libcurl to follow 3xx responses.
- write the doc in doc subfolder for the curl_follow_redirect param

src/modules/http_async_client/doc/http_async_client_admin.xml

@@ -200,6 +200,26 @@ modparam("http_async_client", "curl_verbose", 1)
 </programlisting>
 		</example>
 	</section>
+	<section>
+		<title><varname>curl_follow_redirect</varname> (integer)</title>
+        <para>
+		    If defined to a non-zero value, will tell curl to follow HTTP 3xx redirects.
+		</para>
+		<para>
+		<emphasis>
+			Default value is 0 (disabled).
+		</emphasis>
+		</para>
+		<example>
+		<title>Set <varname>curl_follow_redirect</varname> parameter</title>
+		<programlisting format="linespecific">
+...
+modparam("http_async_client", "curl_follow_redirect", 1)
+...
+</programlisting>
+		</example>
+	</section>
+
 	<section>
 		<title><varname>memory_manager</varname> (string)</title>
         <para>

src/modules/http_async_client/http_async_client_mod.c

@@ -74,6 +74,7 @@ int tls_version = 0; // Use default SSL version in HTTPS requests (see curl/curl
 int tls_verify_host = 1; // By default verify host in HTTPS requests
 int tls_verify_peer = 1; // By default verify peer in HTTPS requests
 int curl_verbose = 0;
+int curl_follow_redirect = 0;
 char* tls_client_cert = NULL; // client SSL certificate path, defaults to NULL
 char* tls_client_key = NULL; // client SSL certificate key path, defaults to NULL
 char* tls_ca_path = NULL; // certificate authority dir path, defaults to NULL
@@ -150,6 +151,7 @@ static param_export_t params[]={
 	{"tls_verify_host",		INT_PARAM,		&tls_verify_host},
 	{"tls_verify_peer",		INT_PARAM,		&tls_verify_peer},
 	{"curl_verbose",		INT_PARAM,		&curl_verbose},
+	{"curl_follow_redirect",	INT_PARAM,		&curl_follow_redirect},
 	{"tls_client_cert",		PARAM_STRING,	&tls_client_cert},
 	{"tls_client_key",		PARAM_STRING,	&tls_client_key},
 	{"tls_ca_path",			PARAM_STRING,	&tls_ca_path},

src/modules/http_async_client/http_multi.c

@@ -462,6 +462,9 @@ int new_request(str *query, http_m_params_t *query_params, http_multi_cbe_t cb,
 		curl_easy_setopt(cell->easy, CURLOPT_VERBOSE, 1L);
 		curl_easy_setopt(cell->easy, CURLOPT_DEBUGFUNCTION, debug_cb);
 	}
+	if (curl_follow_redirect) {
+                curl_easy_setopt(cell->easy, CURLOPT_FOLLOWLOCATION, 1L);
+	}
 	curl_easy_setopt(cell->easy, CURLOPT_ERRORBUFFER, cell->error);
 	curl_easy_setopt(cell->easy, CURLOPT_PRIVATE, cell);
 	curl_easy_setopt(cell->easy, CURLOPT_SSL_VERIFYPEER, cell->params.tls_verify_peer);

src/modules/http_async_client/http_multi.h

@@ -58,6 +58,7 @@ extern stat_var *errors;
 extern stat_var *timeouts;
 extern int tls_version;
 extern int curl_verbose;
+extern int curl_follow_redirect;
 
 void set_curl_mem_callbacks(void);
 int init_http_multi();