复制过来显示错乱了，看上面的图就好
+-------------------+
| Authz Server |
+--------+ | +---------------+ |
| |--(A)- Authorization Request ---->| | |
| | + t(code_verifier), t_m | | Authorization | |
| | | | Endpoint | |
| || | |
| | + code_verifier | | Token | |
| | | | Endpoint | |
| |
