choose which app url facts to use based on request url

Summary:
use getAppURLFactsFromRequestURL to choose which app URL facts to use.

depends on D3406

Test Plan: flow

Reviewers: palys-swm, atul, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, Adrian, karol-bisztyga, benschac

Differential Revision: https://phabricator.ashoat.com/D3413