...
config:auth_scheme=header_token_ukgpro
config:auth_token=<a random 12 character password string that acts as a secure token>
Use this string when configuring webhook in UKG pro - specifically, step 5 of Add Subscription asks you to add a free form headers fields. Set the custom header key to x-onlink-key token and custom header value to the random password string. Note that this random password is encoded once you save the settings and cannot be retrieved back.
...