Backfill feature spec - Invited registration flow

In an effort to have a solid test suite around the existing registration flow, we'd like to backfill the test suite.

• Invite registration flow without tasks
• Invite registration flow with tasks

perhaps the items above can be worked into ee/spec/features/registrations/saas/invite_flow_spec.rb or used for inspiration

Additional information

For some reason the link rendered in the product marketing email doesn’t open the invite members modal anymore. In order to create a task go to /groups/<group_name>/-/group_members?open_modal=invite_members_for_task > select a level > developer.