Fix CORS issues with identity HTTP

Summary: The context is here: https://linear.app/comm/issue/ENG-8806/unable-to-call-identity-http-endpoint-from-service-workerjs-due-to. There were two CORS issues with identity HTTP. This differential applies two fixes from Varun and Will combined

Test Plan: Execute test plan for https://phab.comm.dev/D12703 (D12703). Without changes in this diff it is not possible to succesfully fetch inbound keys from service worker.

Reviewers: varun, will, bartek

Reviewed By: varun, will

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12719