Project Import Testing: verify that all new relations will be tested
It heavily relies on the results of #39536 (closed).
(depending on if we will be able to add all missing relations or will ignore some)
Ideally, it will something similar to !19502 (diffs), where we check that every new relation is also added into Import JSON fixture and tested.
Thus, we will keep supporting "full coverage".
We may go with a spec failure or warning.
We may also allow empty relations if we will find that it is tricky to include some particular relations into a fixture.
Edited by Aleksei Lipniagov