APIv4 - Don't advertise implicit multi-joins in Explorer

[colemanw]

Overview

These joins are problematic and may be removed. The Explorer should not display them.

Before

Now you see them.

After

Now you don't.

Technical Details

This is the first step in deprecation. This doesn't remove support for them, just visibility.

[civibot]

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[colemanw]

@eileenmcnaughton I'd like to get this into 5.25.

[totten]

Policy-wise -- That does seem like a good way to phase it out!

I tried it out on the autobuild site and didn't notice any obvious breakage. The N-to-1 joins (e.g. Contact's current_employer) still showed up. Seems good.

[eileenmcnaughton]

OK - I can accept that while this is not an actual regression, this does fix the case for not advertising something that would up not being doable and an rc hit might save some pain