application - 通用 OTP 应用函数
- get_all_env/0
- get_all_env/1
- get_all_key/0
- get_all_key/1
- get_application/0
- get_application/1
- get_env/1
- get_env/2
- get_key/1
- get_key/2
- info/0
- load/1
- load/2
- loaded_applications/0
- permit/2
- set_env/3
- set_env/4
- start/1
- start/2
- start_type/0
- stop/1
- takeover/2
- unload/1
- unset_env/2
- unset_env/3
- which_applications/0
- which_applications/1