I'm trying to implement the password grant flow, as specified at https://wiki2.dovecot.org/PasswordDatabase/oauth2,

but am getting an error message. Can you please help?

auth: Fatal: oauth2 /etc/dovecot/dovecot-oauth2.token.conf.ext: Error in configuration file /etc/dovecot/dovecot-oauth2.token.conf.ext line 1: Unknown setting: grant_url

$ dovecot -n
# 2.3.5.2 (38c8f1daf): /etc/dovecot/dovecot.conf
# OS: Linux 3.10.0-957.10.1.el7.x86_64 x86_64 CentOS Linux release 7.6.1810 (Core)