Introduce Path Persons API endpoint

[neilkakkar]

Changes

This PR introduces the /api/person/path/ endpoint, which allows querying for users on Paths.

The request expects the same filter as given to Paths, plus two new parameters:

path_start_key and path_end_key. These determine the start and end point of Paths you want. Both of these are optional.

Not specifying them means "get me all users on this path query".

Only specifying path_start_key means "get me all users whose paths start at this key"
Only specifying path_end_key means "get me all users whose paths end at this key"

Specifying both means "get me all users whose path starts at start_key and ends at end_key."

Checklist

• All querysets/queries filter by Organization, by Team, and by User
• Django backend tests
• Jest frontend tests
• Cypress end-to-end tests
• Migrations are safe to run at scale (e.g. PostHog Cloud) – present proof if not obvious
• New/changed UI is decent on smartphones (viewport width around 360px)

[EDsCODE]

👍