fix(cloud-function): strip X-Forwarded-Host + Forwarded headers

[caugner]

Summary

(MP-427)

Problem

http-proxy with xfwd: true only sets x-forwarded-{for,port,proto} and doesn't override x-forwarded-host (see here), which may cause unwanted side-effects.

Solution

Remove x-forwarded-host header (plus forwarded, which may contain a host= directive) in our Cloud Function.

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How did you test this change?

Ran npm start in cloud-function/ and verified that curl -H 'x-forwarded-host: bar http://localhost:5100/fr/?example does not forward the header.

[LeoMcA]

lgtm

[fiji-flo]

Stripping x-forwarded-for can have side effects. Do we need to strip it for this?

[LeoMcA]

@fiji-flo as I understand it, http-proxy won't overwrite an existing x-forwarded-for header, which is why we strip it, then it adds the correct value back in

[LeoMcA]

Looks good, let's put on staging to test it fixes the problem (without causing any others).

Edit: I see you've already kicked off an xyz build

as I understand it, http-proxy won't overwrite an existing x-forwarded-for header, which is why we strip it, then it adds the correct value back in

I misread, it does do the proper thing with x-forwarded-for.