Invite users to use same Developer account via SSO requires second set of credentials

Problem

I want to invite a user to my Developer account whilst allowing the login through RH SSO. It's possible to invite the user and they can complete the 3scale signup form but it's not following the typical SSO flow as credentials are required to complete this form.

Expected behaviour

I invite a user to signup to the 3scale developer portal and join my existing account. The user should be able to create the 3scale user without providing another set of credentials - this should be handled via the SSO integration.

Current behaviour

The new user must complete the 3scale signup form whilst providing a new set of credentials which are ultimately redundant. I can join the account but the flow is confusing and does not follow a typical SSO integration.

Dev notes

When the user clicks on the invite link, the landing page already contains the different SSO instead and the form with password.
Using the SSO does not work. It displays an error message: "The invitation token does not exist"

Question:

• What happens if the email in the invite is not the same email as in the SSO?
  > I think we should trust the SSO, as the user can change its email in the invite landing page.

This needs cucumber tests