feat(plugin): add hook for tunnel

This will enable us to remove tunnel-ssh from the
core and allow developers to even place different
tunnel methods, i.e. proxies or vpns to be put in
place.

Signed-off-by: Tobias Gurtzick <magic@wizardtales.com>

lib/driver/index.js

@@ -18,6 +18,8 @@ var ShadowProto = {
 
 exports.connect = function (config, intern, callback) {
   var driver, req;
+  let plugin = false;
+  const { plugins } = intern;
 
   var mod = internals.mod;
   internals = intern;
@@ -108,9 +110,27 @@ exports.connect = function (config, intern, callback) {
   if (config.tunnel) {
     var tunnel = require('tunnel-ssh');
     var tunnelConfig = JSON.parse(JSON.stringify(config.tunnel));
+    const { tunnelType } = tunnelConfig;
+
+    if (plugins) {
+      plugin = plugins.overwrite(
+        `connection:tunnel:${
+          tunnelType && tunnelType !== 'ssh' ? tunnelType : 'ssh'
+        }`
+      );
+    }
+
     tunnelConfig.dstHost = config.host;
     tunnelConfig.dstPort = config.port;
 
+    if (plugin) {
+      tunnel = plugin[
+        `connection:tunnel:${
+          tunnelType && tunnelType !== 'ssh' ? tunnelType : 'ssh'
+        }`
+      ](tunnelConfig);
+    }
+
     if (tunnelConfig.privateKeyPath) {
       tunnelConfig.privateKey = require('fs').readFileSync(
         tunnelConfig.privateKeyPath