add "ssoRedirectURL" to local.conf

plumbed it through to the central controller code

controller/EmbeddedNetworkController.hpp

@@ -57,6 +57,8 @@ public:
 
 	virtual void init(const Identity &signingId,Sender *sender);
 
+	void setSSORedirectURL(const std::string &url);
+
 	virtual void request(
 		uint64_t nwid,
 		const InetAddress &fromAddr,
@@ -151,6 +153,7 @@ private:
 	std::mutex _memberStatus_l;
 
 	RedisConfig *_rc;
+	std::string _ssoRedirectURL;
 };
 
 } // namespace ZeroTier