Today a user can create a QP with 0 rules and use it on their projects. Which is wonderful because then everything is super green! We shouldn't allow users to enable such Quality Profiles on their project.
When administering a Quality Profile, disable the project assignment and "Set as default" options as long as no rules are enabled, and explain to the user what steps they should take to use this Quality Profile.
When administering a project, disable such Quality Profiles from the list of options, putting a small explanation as to why this profile isn't available.
We will only apply this in the UI. The WS will remain working as before, to avoid changing the WS behavior.