## Is your feature request related to a problem?

/api/person/merge currently performs a merge of two people. This logic is duplicated between app and plugin-server, badly.

## Describe the solution you'd like

Avoid duplicating, send a message to plugin-server

## Describe alternatives you've considered

Duplicating tricky and race-condition-heavy logic.

## Additional context

cc @yakkomajuri this is worth adding to team extensibility backlog - pretty sure this will cause bad correctness issues.

#### *Thank you* for your feature request – we love each and every one!

posthog/api/test/test_person.py
person_factory(
                team=self.team, distinct_ids=["person_1", "anonymous_id"], properties={"$os": "Chrome"},
            )
            person_factory(team=self.team, distinct_ids=["person_2"])
            cohort = Cohort.objects.create(team=self.team, groups=[{"properties": {"$os": "Chrome"}}])
            cohort.calculate_people()
            response = self.client.get(f"/api/person/?cohort={cohort.pk}")
            self.assertEqual(len(response.json()["results"]), 1, response)
        def test_filter_person_list(self):
            person1: Person = person_factory(
                team=self.team,
                distinct_ids=["distinct_id", "another_one"],
                properties={"email": "someone@gmail.com"},
                is_identified=True,
            )
            person2: Person = person_factory(
                team=self.team, distinct_ids=["distinct_id_2"], properties={"email": "another@gmail.com"},