枚举值:authorization_codeimplicitrefresh_tokenclient_credentialspasswordhttp://authok.cn/oauth/grant-type/password-realmhttp://authok.cn/oauth/grant-type/mfa-oobhttp://authok.cn/oauth/grant-type/mfa-otphttp://authok.cn/oauth/grant-type/passwordless/otphttp://authok.cn/oauth/grant-type/mfa-recovery-codeurn:ietf:params:oauth:grant-type:device_code