1, wx.login get the code back to the back-end, back-end and get session_key openid (sometimes bring unionid, sometimes no oh)
2, after the user clicks the button authorized user information, return session_key, encryptedData, iv to the background, the background decrypted user information and unionid (official line is that there must be).
3, the applet must be bound to an open platform can obtain a unionid, the official did not say, but it is 555 ~