The ${ICAL_TMPL} secret variable contents gets added as is to the ICAL event content.
It could contain a list of participants or other extensions to the event details.
Example:
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN={Person Name}:MAILTO:{Person email}
NB: The PARTSTAT=NEEDS-ACTION directive in global ICAL template makes the invitations to be sent out. The PARTSTAT=NEEDS-ACTION;RSVP=TRUE; doesn't really make the gcalcli and Google Calendar to send them as it's expected. Though with some patching of the gcalcli code one can make it work as expected.
I've spent two days on finding this out 🤦
The ${WEB_CREDS} secret variable contains credentials for the CK Sportcenter account.
The following format is expected:
username={username goes here}&password={password goes here}