SSO with FortiWeb (Authentication Delegation)


I am currently trying to configure a FortiWeb as a single sign-on solution, with Nextcloud as one of the services to be accessed via it. There are different types of authentication delegation in connection with FortiWeb, but I assume that “Form Based” is the most suitable (there is also: HTTP Basic, Kerberos and NTLM). Here you would have to specify a "Form Action“ in addition to the Logon URL - and I couldn’t figure out what this form action would be for Nextcloud. As a general explanation in the FortiWeb documentation, it simply says that this is the “URL of the form”… Does anyone in the community have an idea what this would be?

Thanks in advance