I tried to explain our situation already here, but on a second thought I think I got the idea what our key issue is.
https://community.atlassian.com/t5/Confluence-questions/How-to-set-up-permissions-differently-for-parnter-and-customer/qaq-p/756267
I need to enable the public signup for JIRA Service Desk (JSD), because the user should be able to do so + a user should be created if an email is sent to the JSD project.
I also need Confluence KB to be connected to the JSD project, as it would not make sens for us to switch to JSD without using the KB. To use this feature without giving licenses to every customer I think the Confluence KB space must be connected to the JSD project.
THE CHALLENGE: I must not allow the newly signed up user to access the Confluence KB space from the very beginning as we have to verify first that it is one of our customers.
It seems to me that this is simply not possible. Is there any chance to do this?