1. The client needs to call the WeChat interface to obtain the code, encryptedData, iv, and this code needs to be passed to the server;
2. The server calls the relevant interface of WeChat, passes the code as a parameter, and obtains the open_id (the unique identifier of the user in the applet) and session_key;
3. encryptedData is the encrypted data of user information, the server can decrypt encryptedData data through session_key and iv.
The above is the general process of WeChat applet login.
