Dedupe geonames self parent

[orangejulius]

this PR is branched off of #1606, since we'll likely merge that one first. comparison for only this PR is here

Background

In pelias/geonames#93 we added some special case logic to the Geonames importer that ensures Geonames records in the locality and localadmin layer have themselves as parents in that layer.

Before this change, they would have a Who's on First parent, but these parents didn't always line up perfectly. Sometimes it would lead to broken labels, and as I recall it could also break search queries that rely on locality/localadmin names.

Hierarchy checks

This special logic causes problems with our hierarchy checks, which expect records that can be considered duplicates to share all parents higher than the lower record.

So for example, if a locality and localadmin are to be considered duplicates, the hierarchy must be the same from the country layer down to localadmin.

Geonames localadmins

Geonames seems to have a penchant for having both a locality and a localadmin record for a given city, even when the local administrative divisions don't really support such nuance.

These records often have a name following the format 'City of X', which makes them very disruptive and confusing when shown in a list of results.

Deduplication

Our deduplication code can handle minor name differences like 'City of' after #1371, but can't handle the hierarchy differences that generally occur with these records.

Generally, there will be one of two scenarios:

• A WOF locality record for the city can't deduplicate with the Geonames localadmin because the WOF record is parented by a WOF localadmin
• A WOF locality record for the city can't deduplicate with the Geonames localadmin because the WOF record has no localadmin parent at all

Concordances (from #1606) generally don't help either, since there often isn't a localadmin in WOF to even have a concordance to the Geonames localadmin.

Adding a hierarchy exception

This PR works by skipping the hierarchy checks for any layer where a Geonames record has itself as a parent. This means that assuming all the other layers are the same, the names are compatible, etc, deduplication is still possible.

Impact

Of the 314 cities in our top_us_cities fuzzy tests, most of them (125) had a 'City of X' record somewhere in the results when querying via the autocomplete endpoint.

With this PR, there are only 15 cases.

Potential regressions

Theoretically, this could allow records that aren't actually duplicates to be deduped, but they would have to have a similar name and likely share at least a county, so it feels like the chance for error is
limited.

That said, there are no regressions in our acceptance tests, and quite a few improvements.